Update MAINTAINERS.md (#122)

Removing old maintainers of this project; no longer active -- I tried to reach them for the last 6 months or so.

Please speak up if you would like to continue the activity and be on this list - thanks for all your work!

@roidelapluie @onprem @arajkumar

Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>

Author: bwplotka

MAINTAINERS.md

@@ -1,5 +1,2 @@
-* Arunprasad Rajkumar <ar.arunprasad@gmail.com> @arajkumar
-* Prem Saraswat <prmsrswt@gmail.com> @onprem
-* Julien Pivotto <roidelapluie@prometheus.io> @roidelapluie
 * Bartek Płotka <bwplotka@gmail.com> @bwplotka
 * Saswata Mukherjee <saswata.mukhe@gmail.com> @saswatamcode