docs(backups): state when the gate compares endpoints in the values reference

The values reference read as if the credentials endpoint were always
compared and an object without the endpoint annotation never forced a
render. Operators sizing the force counter or choosing a custom
systemSecretName need both conditions spelled out.

Assisted-by: LLM
Signed-off-by: Alexey Artamonov <aleksei.artamonov@aenix.io>

packages/system/backupstrategy-controller/values.yaml

@@ -164,10 +164,12 @@ backupStorage:
   # cozy-default routes to exists and forces THIS release when any is
   # missing. It repairs a stale S3 endpoint the same way: when the
   # credentials Secret's endpoint differs from the COSI Secret it is rendered
-  # from it forces the bucket's <bucket>-system release, and when the
+  # from it forces the bucket's <bucket>-system release (only while
+  # systemSecretName is bucket-<bucketName>-system-credentials, the one
+  # Secret that release renders), and when the
   # backups.cozystack.io/endpoint annotation on the Velero BSL or a default
-  # Strategy differs from the credentials Secret's endpoint it forces THIS
-  # release. The COSI Secret itself keeps the endpoint it was granted with, so
+  # Strategy differs from the credentials Secret's endpoint, or is absent, it
+  # forces THIS release. The COSI Secret itself keeps the endpoint it was granted with, so
   # after a publishing.host change that endpoint follows only once the
   # BucketAccess is re-granted. Both are throttled, independently, and a no-op
   # in the steady state. A suspended release is skipped rather than