runtime(compiler): fix inaccuracies in pandoc compiler (#14467)

as kindly pointed out by @Freed-Wu

Signed-off-by: Enno <Konfekt@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/compiler/pandoc.vim b/runtime/compiler/pandoc.vim
index a536257..1b171a1 100644
--- a/runtime/compiler/pandoc.vim
+++ b/runtime/compiler/pandoc.vim
@@ -9,10 +9,6 @@
   finish
 endif
 
-if exists(":CompilerSet") != 2		" older Vim always used :setlocal
-  command -nargs=* CompilerSet setlocal <args>
-endif
-
 let s:keepcpo = &cpo
 set cpo&vim
 
@@ -40,9 +36,9 @@
   elseif ft ==# 'text' || empty(ft)
     return 'markdown'
   elseif index(s:supported_filetypes, &ft) >= 0
-    return ft
+      return ft
   else
-    echomsg 'Unsupported filetype: ' . a:filetype ', falling back to Markdown as input format!'
+    echomsg 'Unsupported filetype: ' . ft . ', falling back to Markdown as input format!'
     return 'markdown'
   endif
 endfunction