patch 8.2.2060: check for features implemented with "if"

Problem:    Check for features implemented with "if".
Solution:   Use the Check commands. (Ken Takata, closes #7383)
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index c51f37f..1873a7a 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -1689,9 +1689,7 @@
 endfunc
 
 func Test_Filter_noshelltemp()
-  if !executable('cat')
-    return
-  endif
+  CheckExecutable cat
 
   enew!
   call setline(1, ['a', 'b', 'c', 'd'])