MAINTAINERS: remove Brandon Philips @philips

I have not been active in the project for quite some time so I am
stepping down.

Thank you for all of the work over the years to standardize container
formats everyone!

MAINTAINERS

@@ -1,4 +1,3 @@
-Brandon Philips <[email protected]> (@philips)
 Brendan Burns <[email protected]> (@brendandburns)
 Jason Bouzane <[email protected]> (@jbouzane)
 John Starks <[email protected]> (@jstarks)