patch 8.2.1432: various inconsistencies in test files

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)
diff --git a/src/testdir/test_menu.vim b/src/testdir/test_menu.vim
index 38098a1..033d428 100644
--- a/src/testdir/test_menu.vim
+++ b/src/testdir/test_menu.vim
@@ -62,9 +62,7 @@
 endfunc
 
 func Test_translate_menu()
-  if !has('multi_lang')
-    return
-  endif
+  CheckFeature multi_lang
   if !filereadable($VIMRUNTIME . '/lang/menu_de_de.latin1.vim')
     throw 'Skipped: translated menu not found'
   endif