runtime: Remove fallback :CompilerSet definition from compiler plugins

The :CompilerSet command was added in version Vim 6.4 which was released
twenty years ago.  Other runtime files do not support versions of that
vintage so it is reasonable to remove this fallback command definition
now.

closes: #14399

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/compiler/eslint.vim b/runtime/compiler/eslint.vim
index 7d57acb..db7a665 100644
--- a/runtime/compiler/eslint.vim
+++ b/runtime/compiler/eslint.vim
@@ -2,15 +2,12 @@
 " Compiler:    ESLint for JavaScript
 " Maintainer:  Romain Lafourcade <romainlafourcade@gmail.com>
 " Last Change: 2020 August 20
+"	       2024 Apr 03 by The Vim Project (removed :CompilerSet definition)
 
 if exists("current_compiler")
   finish
 endif
 let current_compiler = "eslint"
 
-if exists(":CompilerSet") != 2
-  command -nargs=* CompilerSet setlocal <args>
-endif
-
 CompilerSet makeprg=npx\ eslint\ --format\ compact
 CompilerSet errorformat=%f:\ line\ %l\\,\ col\ %c\\,\ %m,%-G%.%#