runtime(misc): unset compiler in various ftplugins

just to foster best practices

closes: #15798

Signed-off-by: Konfekt <Konfekt@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/rust.vim

@@ -148,6 +148,7 @@ endif
 " Cleanup {{{1
 
 let b:undo_ftplugin = "
+            \ compiler make |
             \ setlocal formatoptions< comments< commentstring< include< includeexpr< suffixesadd<
             \|if exists('b:rust_set_style')
                 \|setlocal tabstop< shiftwidth< softtabstop< expandtab< textwidth<