Remove Eng Prod metricbeats tests ownership (elastic#41597)

Author: rowlandgeoff

.github/CODEOWNERS

@@ -105,7 +105,6 @@ CHANGELOG*
 /metricbeat/module/system/ @elastic/elastic-agent-data-plane
 /metricbeat/module/vsphere @elastic/obs-infraobs-integrations
 /metricbeat/module/zookeeper @elastic/obs-infraobs-integrations
-/metricbeat/tests @elastic/ingest-eng-prod
 /packetbeat/ @elastic/sec-linux-platform
 /script/ @elastic/elastic-agent-data-plane
 /testing/ @elastic/elastic-agent-data-plane