Big Bang Bot: Update CODEOWNERS

Action	User	Reason
Remove	@micah.nagel	Employment dates no longer active
Remove	@ryan.j.garcia	Employment dates no longer active
Remove	@dylan.anderson	Username is not present in either team or contributor whitelist.
Remove	@bwijayaw	Username is not present in either team or contributor whitelist.
Remove	@ninonocita	Username is not present in either team or contributor whitelist.
---------	---------	-----------
Error	@	Too few codeowners, minimum is: 3

These changes were automatically generated based on the state stored in the team charter mission team manifest. If these changes are not expected, please refer to updating team charter manifest.