Differential: Rename "Foist Upon" to "Change Author"

Summary:
Use terms which actually communicate which aspect of a revision will be changed by performing an action.
(I rate clarity of outcomes of actions higher than being forced to interpret ambiguous vocabulary.)

Most action dropdown items are already prefixed with "Change $something".
The existing code in `DifferentialRevisionAuthorTransaction` already fell back to "changed the author of this revision" before this very change.

Closes T16301

Test Plan:
* Look at the options in the action dropdown in a Differential revision
* Foist upon someone, look at the log entries

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T16301

Differential Revision: https://we.phorge.it/D26428

src/applications/differential/editor/DifferentialRevisionEditEngine.php

···
       ->setDatasource(new PhabricatorPeopleDatasource())
       ->setTransactionType(
         DifferentialRevisionAuthorTransaction::TRANSACTIONTYPE)
-      ->setDescription(pht('Foist this revision upon someone else.'))
-      ->setConduitDescription(pht('Foist this revision upon another user.'))
+      ->setDescription(pht('Make someone else the author of this revision.'))
+      ->setConduitDescription(
+        pht('Make another user the author of this revision.'))
       ->setConduitTypeDescription(pht('New author.'))
       ->setSingleValue($object->getAuthorPHID());
 
···
       $author_field->setIsHidden(true);
     }
 
-    // Only show the "Foist Upon" comment action to the current revision
-    // author. Other users can use "Edit Revision", it's just very unlikley
+    // Only show the "Change Author" comment action to the current revision
+    // author. Other users can use "Edit Revision", it's just very unlikely
     // that they're interested in this action.
     if ($viewer->getPHID() === $object->getAuthorPHID()) {
-      $author_field->setCommentActionLabel(pht('Foist Upon'));
+      $author_field->setCommentActionLabel(pht('Change Author'));
     }
 
     $fields[] = $author_field;

src/applications/differential/xaction/DifferentialRevisionAuthorTransaction.php

···
     if ($is_foist) {
       if ($new_phid) {
         return pht(
-          '%s foisted this revision upon %s.',
+          '%s changed the author of this revision to %s.',
           $this->renderAuthor(),
           $this->renderNewHandle());
       } else {
···
         // the preview if you temporarily delete the tokenizer value.
 
         return pht(
-          '%s foisted this revision upon...',
+          '%s changed the author of this revision to...',
           $this->renderAuthor());
       }
     }