[chore] Update codeowners for groupbyattrsprocessor (open-telemetry#2…

…3414)

Updating CODEOWNERS for processor/groupbyattrsprocessor

.github/CODEOWNERS

@@ -137,7 +137,7 @@ processor/cumulativetodeltaprocessor/ @open-telemetry/collect
 processor/datadogprocessor/ @open-telemetry/collector-contrib-approvers @mx-psi @gbbr @dineshg13
 processor/deltatorateprocessor/ @open-telemetry/collector-contrib-approvers @Aneurysm9
 processor/filterprocessor/ @open-telemetry/collector-contrib-approvers @TylerHelmuth @boostchicken
-processor/groupbyattrsprocessor/ @open-telemetry/collector-contrib-approvers
+processor/groupbyattrsprocessor/ @open-telemetry/collector-contrib-approvers @rnishtala-sumo
 processor/groupbytraceprocessor/ @open-telemetry/collector-contrib-approvers @jpkrohling
 processor/k8sattributesprocessor/ @open-telemetry/collector-contrib-approvers @dmitryax @rmfitzpatrick @fatsheep9146
 processor/logstransformprocessor/ @open-telemetry/collector-contrib-approvers @djaglowski @dehaansa