Do not create search_documentfield table; update docs

Summary:
Per rP719dd6d3f44245e935b21291a59338a819938c49 and previous rP6cedd4a95cfc23a1679400fb64863c49f24f2306, remove the `search_documentfield` table from initial creation (`quickstart.sql`) and Diviner database docs.

Pointed out in Q82.

Additional context:
MySQL 5.6.4 released 2011-12-20 "now supports FULLTEXT indexes for InnoDB tables" per https://forums.mysql.com/read.php?3,506409 and per https://downloads.mysql.com/docs/mysql-5.6-relnotes-en.pdf pages 230 and 233.
Per https://www.oracle.com/us/support/library/lifetime-support-technology-069183.pdf page 29, "Extended Support Ends" for "MySQL Database 5.6" in "Feb 2021".
MariaDB went for version 10 instead of 5.6 per https://mariadb.org/mariadb-10-0-and-mysql-5-6/; MariaDB 10.0 saw its End of Life date on "31 Mar 2019" per https://mariadb.org/about/#maintenance-policy

Test Plan:
* As an admin, go to `/config/issue/` which triggers `PhabricatorSetupCheck::runNormalChecks()` and thus runs database checks.
* Install a fresh instance of Phorge which runs quickstart.sql, for example setting `"storage.default-namespace": "test"` inside `conf/local/local.json` and see that things still works, like Phriction search by name etc.

Reviewers: O1 Blessed Committers, mainframe98, valerio.bozzolan

Reviewed By: O1 Blessed Committers, mainframe98, valerio.bozzolan

Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25895

resources/sql/quickstart.sql

···
 
  SET character_set_client = {$CHARSET} ;
 
-CREATE TABLE `search_documentfield` (
-  `phid` varbinary(64) NOT NULL,
-  `phidType` varchar(4) CHARACTER SET {$CHARSET} COLLATE {$COLLATE_TEXT} NOT NULL,
-  `field` varchar(4) CHARACTER SET {$CHARSET} COLLATE {$COLLATE_TEXT} NOT NULL,
-  `auxPHID` varbinary(64) DEFAULT NULL,
-  `corpus` longtext CHARACTER SET {$CHARSET_FULLTEXT} COLLATE {$COLLATE_FULLTEXT},
-  `stemmedCorpus` longtext CHARACTER SET {$CHARSET_SORT} COLLATE {$COLLATE_SORT},
-  KEY `phid` (`phid`),
-  FULLTEXT KEY `key_corpus` (`corpus`,`stemmedCorpus`)
-) ENGINE=MyISAM DEFAULT CHARSET={$CHARSET} COLLATE={$COLLATE_TEXT};
-
-USE `{$NAMESPACE}_search`;
-
- SET NAMES utf8 ;
-
- SET character_set_client = {$CHARSET} ;
-
 CREATE TABLE `search_documentrelationship` (
   `phid` varbinary(64) NOT NULL,
   `relatedPHID` varbinary(64) NOT NULL,

src/applications/config/check/PhabricatorMySQLSetupCheck.php

···
           "(in the %s section) and then restart %s:\n\n".
           "%s\n".
           "(You can also use a different file if you prefer. The file ".
-          "suggested above has about 50 of the most common English words.)\n\n".
-          "Finally, run this command to rebuild indexes using the new ".
-          "rules:\n\n".
-          "%s",
+          "suggested above has about 50 of the most common English words.)",
           $host_name,
           phutil_tag('tt', array(), 'my.cnf'),
           phutil_tag('tt', array(), '[mysqld]'),
           phutil_tag('tt', array(), 'mysqld'),
-          phutil_tag('pre', array(), 'ft_stopword_file='.$stopword_path),
-          phutil_tag(
-            'pre',
-            array(),
-            "mysql> REPAIR TABLE {$namespace}_search.search_documentfield;"));
+          phutil_tag('pre', array(), 'ft_stopword_file='.$stopword_path));
 
         $this->newIssue('mysql.ft_stopword_file')
           ->setName(pht('MySQL is Using Default Stopword File'))
···
           "only MySQL fulltext search is affected.\n\n".
           "To reduce the minimum word length to 3, add this to your %s file ".
           "(in the %s section) and then restart %s:\n\n".
-          "%s\n".
-          "Finally, run this command to rebuild indexes using the new ".
-          "rules:\n\n".
-          "%s",
+          "%s\n",
           $host_name,
           phutil_tag('tt', array(), 'my.cnf'),
           phutil_tag('tt', array(), '[mysqld]'),
           phutil_tag('tt', array(), 'mysqld'),
-          phutil_tag('pre', array(), 'ft_min_word_len=3'),
-          phutil_tag(
-            'pre',
-            array(),
-            "mysql> REPAIR TABLE {$namespace}_search.search_documentfield;"));
+          phutil_tag('pre', array(), 'ft_min_word_len=3'));
 
         $this->newIssue('mysql.ft_min_word_len')
           ->setName(pht('MySQL is Using Default Minimum Word Length'))

src/docs/contributor/database.diviner

···
 Phorge uses MySQL or another MySQL-compatible database (like MariaDB
 or Amazon RDS).
 
-Phorge uses the InnoDB table engine. The only exception is the
-`search_documentfield` table which uses MyISAM because MySQL doesn't support
-fulltext search in InnoDB (recent versions do, but we haven't added support
-yet).
+Phorge uses the InnoDB table engine.
 
 We are unlikely to ever support other incompatible databases like PostgreSQL or
 SQLite.