Pin microshift build for openshift-4.16 4.16.20

Created by job run https://art-jenkins.apps.prod-stable-spoke1-dc-iad2.itup.redhat.com/job/aos-cd-builds/job/build%252Fbuild-microshift/1308

releases.yml

@@ -49,7 +49,12 @@ releases:
             is:
               nvr: openshift-enterprise-tests-container-v4.16.0-202410300036.p0.g06403d4.assembly.stream.el9
           why: Query from assembly basis event failed to replicate referenced nightly content exactly. Pinning to replicate.
-        rpms: []
+        rpms:
+        - distgit_key: microshift
+          why: Pin microshift to assembly
+          metadata:
+            is:
+              el9: microshift-4.16.20-202410310940.p0.g421a104.assembly.4.16.20.el9
       rhcos:
         rhel-coreos:
           images: