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
diff --git a/releasenotes/notes/use-metadata-grouping-for-prometheus-autoscaling-763c98141a940531.yaml b/releasenotes/notes/use-metadata-grouping-for-prometheus-autoscaling-763c98141a940531.yaml
new file mode 100644
index 0000000..b046fe9
--- /dev/null
+++ b/releasenotes/notes/use-metadata-grouping-for-prometheus-autoscaling-763c98141a940531.yaml
@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Added ability to use metadata instance grouping when testing prometheus based autoscaling.
+    This method of instance grouping is supported since 2025.1 and it's the default option.
+    The ``autoscaling_instance_grouping`` configuration option has been added, which switches
+    the grouping method between ``metadata`` grouping and ``instance`` grouping.