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_regexp_latin.vim b/src/testdir/test_regexp_latin.vim
index 8df357f..9acb12b 100644
--- a/src/testdir/test_regexp_latin.vim
+++ b/src/testdir/test_regexp_latin.vim
@@ -1149,7 +1149,7 @@
   # matchstr().
   enew
   setline(1, ['one', 'two', 'three'])
-  :3 
+  :3
   :/ee
   bwipe!
   set re=1