Fix Gerrit image name

Change If582c0c7a050c176e95d18b51bcff65cc2bf14ce accidentally bumped the
almalinux version.

Set almalinux back to version 8.

Change-Id: I70ad1bcf4493386d2d105a56d2debe7042353efa
diff --git a/gerrit/Dockerfile b/gerrit/Dockerfile
index 6781232..c42f159 100644
--- a/gerrit/Dockerfile
+++ b/gerrit/Dockerfile
@@ -1,7 +1,7 @@
 ARG GERRIT_VERSION
 ARG GERRIT_PATCH
 ARG GERRIT_WAR_URL
-FROM gerritcodereview/gerrit:$GERRIT_VERSION.$GERRIT_PATCH-almalinux9
+FROM gerritcodereview/gerrit:$GERRIT_VERSION.$GERRIT_PATCH-almalinux8
 
 ARG withXRay=false