Revert the shell version to 8.0.21

Change-Id: Ia18dc4d56443c4721b0590267064eba610808bdd

Author: bkandasa

VERSION

@@ -6,7 +6,7 @@ MYSQL_CLUSTER_VERSIONS["8.0"]=8.0.22
 declare -A MYSQL_SHELL_VERSIONS
 MYSQL_SHELL_VERSIONS["7.5"]=8.0.22
 MYSQL_SHELL_VERSIONS["7.6"]=8.0.22
-MYSQL_SHELL_VERSIONS["8.0"]=8.0.22
+MYSQL_SHELL_VERSIONS["8.0"]=8.0.21
 
 declare -A SERVER_VERSION_FULL
 SERVER_VERSION_FULL["7.5"]="${MYSQL_CLUSTER_VERSIONS["7.5"]}-${IMAGE_VERSION}"