Make automatic Redis enabling safer, when Hookshot encryption enabled

If we ever default encryption to enabled for Hookshot, we only wish to force-enable Redis if Hookshot is actually enabled.

group_vars/matrix_servers

@@ -3359,7 +3359,7 @@ ntfy_visitor_request_limit_exempt_hosts_hostnames_auto: |
 #
 ######################################################################
 
-redis_enabled: "{{ matrix_synapse_workers_enabled or matrix_hookshot_experimental_encryption_enabled }}"
+redis_enabled: "{{ matrix_synapse_workers_enabled or (matrix_hookshot_enabled and matrix_hookshot_experimental_encryption_enabled) }}"
 
 redis_identifier: matrix-redis