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/summarize.vim b/src/testdir/summarize.vim
index da5856a..d0d4e00 100644
--- a/src/testdir/summarize.vim
+++ b/src/testdir/summarize.vim
@@ -33,7 +33,7 @@
     silent %s/^SKIPPED \zs.*/\=Count(submatch(0), 'skipped')/egn
     silent %s/^\(\d\+\)\s\+FAILED:/\=Count(submatch(1), 'failed')/egn
 
-    call extend(output, ["Skipped:"]) 
+    call extend(output, ["Skipped:"])
     call extend(output, skipped_output)
 
     call extend(output, [