Assign new gz-sim maintainer (#3008)

Signed-off-by: Addisu Z. Taddese <[email protected]>
(cherry picked from commit 6a2df65)

Author: azeey

.github/CODEOWNERS

@@ -1,7 +1,7 @@
 # More info:
 # https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners
 
-*                     @mjcarroll
+*                     @arjo129
 */rendering/*         @iche033
 src/systems/physics/* @azeey
 src/systems/sensors/* @iche033

README.md

@@ -1,6 +1,6 @@
 # Gazebo Sim : A Robotic Simulator
 
-**Maintainer:** michael AT openrobotics DOT org
+**Maintainer:** arjoc AT intrinsic DOT ai
 
 [![GitHub open issues](https://img.shields.io/github/issues-raw/gazebosim/gz-sim.svg)](https://github.com/gazebosim/gz-sim/issues)
 [![GitHub open pull requests](https://img.shields.io/github/issues-pr-raw/gazebosim/gz-sim.svg)](https://github.com/gazebosim/gz-sim/pulls)