Fixes the `objc_keywords` list in `check_diff_for_keywords`.
This list stores strings and Python automagically concatenates strings if there is no comma between them.
As a result the first two items of the list: `OWSAbstractMethod\(` and `OWSAssert\(` were wrongly conacatenated into `"OWSAbstractMethod\(OWSAssert\("`.
This has been found with LGTM 0ddaedbfad/files/Scripts/precommit.py (x84c147336239d4b6):1