Added updates dir for Fedora 31 release

Patch set [1] does not provide updates directory for
Fedora 31 which is required to run CI jobs.

[1] https://review.opendev.org/#/c/712680/

Change-Id: I01b9b50660f3c7a3b4eb05cc8a8c0847f47dc7ee

playbooks/roles/mirror-update/files/fedora-mirror-update

@@ -72,7 +72,7 @@ for REPO in releases/29 releases/30 releases/31; do
     echo_ts "... done"
 done
 
-for REPO in updates/29 updates/30; do
+for REPO in updates/29 updates/30 updates/31; do
     if ! [ -f $BASE/$REPO ]; then
         $K5START mkdir -p $BASE/$REPO
     fi