[Backport 2.x] v2.12 update roles.yml with new API for experimental a…

…lerting plugin feature (#4035)

Backport ca4eedf from #4027.

Signed-off-by: AWSHurneyt <hurneyt@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

config/roles.yml

@@ -33,6 +33,7 @@ alerting_read_access:
     - 'cluster:admin/opendistro/alerting/monitor/get'
     - 'cluster:admin/opendistro/alerting/monitor/search'
     - 'cluster:admin/opensearch/alerting/findings/get'
+    - 'cluster:admin/opensearch/alerting/remote/indexes/get'
     - 'cluster:admin/opensearch/alerting/workflow/get'
     - 'cluster:admin/opensearch/alerting/workflow_alerts/get'