Metadata grouping releasenote

This adds a releasenote about changes done in:
https://review.opendev.org/c/openstack/telemetry-tempest-plugin/+/932548
https://review.opendev.org/c/openstack/telemetry-tempest-plugin/+/930487

Change-Id: Ie8abc3ebcfc606b4c3aa588998a4b74b42ee9787
1 file changed