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/fpc.vim b/runtime/compiler/fpc.vim
index de8e2fe..0d321ab 100644
--- a/runtime/compiler/fpc.vim
+++ b/runtime/compiler/fpc.vim
@@ -2,16 +2,13 @@
 " Compiler:     FPC 2.1
 " Maintainer:   Jaroslaw Blasiok <jaro3000@o2.pl>
 " Last Change:  2005 October 07
+"               2024 Apr 03 by The Vim Project (removed :CompilerSet definition)
 
 if exists("current_compiler")
   finish
 endif
 let current_compiler = "fpc"
 
-if exists(":CompilerSet") != 2		" older Vim always used :setlocal
-  command -nargs=* CompilerSet setlocal <args>
-endif
-
 " NOTE: compiler must be run with -vb to write whole source path, not only file
 " name.
 CompilerSet errorformat=%f(%l\\,%c)\ %m