patchcheck: don’t talk about the test suite when no code file were changed.

The line about the test suite will still get printed for changes in
Tools for example, which aren’t covered by the test suite, but it’s not
a big deal IMO.

Tools/scripts/patchcheck.py

@@ -157,8 +157,9 @@ def main():
     reported_news(special_files)
 
     # Test suite run and passed.
-    print()
-    print("Did you run the test suite?")
+    if python_files or c_files:
+        print()
+        print("Did you run the test suite?")
 
 
 if __name__ == '__main__':