patch 9.0.2093: Unsupported option causes skipping of modeline test

Problem:  Unsupported option causes rest of modeline test to be skipped.
Solution: Revert the change from patch 8.2.1432.

closes: #13499
closes: #13500

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_modeline.vim b/src/testdir/test_modeline.vim
index 9fb233c..0a7240b 100644
--- a/src/testdir/test_modeline.vim
+++ b/src/testdir/test_modeline.vim
@@ -164,7 +164,11 @@
 endfunc
 
 func s:modeline_fails(what, text, error)
-  call CheckOption(a:what)
+  " Don't use CheckOption(), it would skip the whole test
+  " just for a single un-supported option
+  if !exists('+' .. a:what)
+    return
+  endif
   let fname = "Xmodeline_fails_" . a:what
   call writefile(['vim: set ' . a:text . ' :', 'nothing'], fname, 'D')
   let modeline = &modeline