Remove svn artefacts from MAINTAINERS

[ceri]

Summary

MAINTAINERS still contains references to how LOCKS used to work in svn.
I don't think LOCKS is programmatically enforced now (couldn't find anything in .git anyway).

While in here, remove an unneeded comma.

Test Plan

N/A

[emaste]

We do have git hooks that enforce commit requirements, e.g. for commits to releng branches. @lwhsu can comment.