scripted-diff: Use new python 3.7 keywords

-BEGIN VERIFY SCRIPT-
 sed -i 's/universal_newlines/text/g' $(git grep -l universal_newlines)
-END VERIFY SCRIPT-

contrib/devtools/clang-format-diff.py

@@ -146,7 +146,7 @@ def main():
                          stdout=subprocess.PIPE,
                          stderr=None,
                          stdin=subprocess.PIPE,
-                         universal_newlines=True)
+                         text=True)
     stdout, stderr = p.communicate()
     if p.returncode != 0:
       sys.exit(p.returncode)