tree-sitter-grammars: remove fluent as it is abandoned

pkgs/development/tools/parsing/tree-sitter/grammars/default.nix

···
   tree-sitter-erlang = lib.importJSON ./tree-sitter-erlang.json;
   tree-sitter-fennel = lib.importJSON ./tree-sitter-fennel.json;
   tree-sitter-fish = lib.importJSON ./tree-sitter-fish.json;
-  tree-sitter-fluent = lib.importJSON ./tree-sitter-fluent.json;
   tree-sitter-fortran = lib.importJSON ./tree-sitter-fortran.json;
   tree-sitter-gdscript = lib.importJSON ./tree-sitter-gdscript.json;
   tree-sitter-glimmer = lib.importJSON ./tree-sitter-glimmer.json;

pkgs/development/tools/parsing/tree-sitter/grammars/tree-sitter-fluent.json

···
-{
-  "url": "https://github.com/tree-sitter/tree-sitter-fluent",
-  "rev": "858fdd6f1e81992e00d3541bfb31bac9365d7a47",
-  "date": "2018-06-18T13:00:38-07:00",
-  "path": "/nix/store/zbj8abdlrqi9swm8qn8rhpqmjwcz145f-tree-sitter-fluent",
-  "sha256": "0528v9w0cs73p9048xrddb1wpdhr92sn1sw8yyqfrq5sq0danr9k",
-  "fetchLFS": false,
-  "fetchSubmodules": false,
-  "deepClone": false,
-  "leaveDotGit": false
-}

pkgs/development/tools/parsing/tree-sitter/update.nix

···
     "tree-sitter-scala"
     "tree-sitter-ocaml"
     "tree-sitter-julia"
-    "tree-sitter-fluent"
     "tree-sitter-html"
     "tree-sitter-haskell"
     "tree-sitter-regex"
···
     "tree-sitter-swift"
     # abandoned
     "tree-sitter-agda"
+    # abandoned
+    "tree-sitter-fluent"
   ];
   ignoredTreeSitterOrgReposJson = jsonFile "ignored-tree-sitter-org-repos" ignoredTreeSitterOrgRepos;