doc: fix lint nits in COLLABORATOR_GUIDE.md
Checklist
-
make -j4 test(UNIX), orvcbuild test(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
To unbreak the doc linting)
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
make -j4 test (UNIX), or vcbuild test (Windows) passesTo unbreak the doc linting)