obslog: remove now-unused code for plain styling We now always use a non-plain formatter for the non-local-filtering code paths, so we can remove the code for plain styling. I couldn't figure out how to replace the fm.formatlist() by something less about formatting, so I've only removed the irrelevant arguments from those calls.

{"pattern": "glob:hgext3rd/**/*.py", "tool": "byteify-strings"}