Fixed: downgrade metallb version from 0.13.4 to 0.12.1

To prevent bugs:
- metallb/metallb#1540
- metallb/metallb#1547

cluster/core/networking/metallb/metallb.yaml

@@ -1,22 +1,4 @@
 ---
-apiVersion: metallb.io/v1beta1
-kind: L2Advertisement
-metadata:
-  name: l2-ip
-  namespace: networking
-spec:
-  ipAddressPools:
-    - default-pool
----
-apiVersion: metallb.io/v1beta1
-kind: IPAddressPool
-metadata:
-  name: default-pool
-  namespace: networking
-spec:
-  addresses:
-    - 192.168.1.200-192.168.1.250
----
 apiVersion: helm.toolkit.fluxcd.io/v2beta1
 kind: HelmRelease
 metadata:
@@ -27,9 +9,16 @@ spec:
   chart:
     spec:
       chart: metallb
-      version: 0.13.4
+      version: 0.12.1
       sourceRef:
         kind: HelmRepository
         name: metallb-charts
         namespace: flux-system
       interval: 5m
+  values:
+    configInline:
+      address-pools:
+        - name: default
+          protocol: layer2
+          addresses:
+            - 192.168.1.200-192.168.1.250