Add alert for net-snmp

package_alerts/prod.packages.yml

 # The packages dictionary is a mapping of package names to a dictionary of
 # attributes.  The possible attributes are:
-#   feed: The name of the feed (or a regular expression) to look for this package in.
+#   feed: The name of the feed (or a regular expression, like `(rhel|almalinux)-9-.*`) to look for this package in.
 #   notes: A string containing notes about this package. May be a multi-line string and include markdown.
 # Both attributes are optional, if they're not present then all feeds will be matched
 # and no notes will be included in the MM message.
@@ -26,3 +26,7 @@ packages:
   mod_security_crs:
     notes: |-
       We should confirm if the [workaround](https://gitlab.cern.ch/ai/it-puppet-hostgroup-lxsoft/-/merge_requests/289) is no longer required with this update
+  net-snmp:
+    feed: (rhel|almalinux)-9-.*
+    notes: |-
+      We're waiting for `5.9.1-16` (which should fix [this issue](https://access.redhat.com/solutions/7070455), [RHEL-40403](https://issues.redhat.com/browse/RHEL-40403)). Inform Veronique and Lionel in [INC3963608](https://cern.service-now.com/service-portal?id=ticket&n=INC3963608).
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