patch 9.0.1257: code style is not check in test scripts

Problem:    Code style is not check in test scripts.
Solution:   Add basic code style check for test files.
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index ec824b0..9caa931 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -2072,7 +2072,7 @@
   file %%%%%%%%%%%%%%%%%%%%%%%%%%
   file %%%%%%
   set readonly
-  set ls=2 
+  set ls=2
 
   redraw!
   set noreadonly ls&