Add Rob Murray (@robmry) as maintainer

Rob is currently a curator, and has been actively contributing to this
repo for 7 months now.

Beside day-to-day triaging and bug fixing, Rob is an instrumental
contributor to libnetwork, and amongst other things, to the ongoing work
on IPv6 improvements.

I nominated Rob as maintainer, and votes passed, so opening a PR to make
it official.

Signed-off-by: Albin Kerouanton <albinker@gmail.com>

MAINTAINERS

@@ -38,6 +38,7 @@
 			"laurazard",
 			"mhbauer",
 			"neersighted",
+			"robmry",
 			"rumpl",
 			"runcom",
 			"samuelkarp",
@@ -75,7 +76,6 @@
 			"olljanat",
 			"programmerq",
 			"ripcurld",
-			"robmry",
 			"sam-thibault",
 			"samwhited",
 			"thajeztah"