Revert "chore(syncthing): try just mounting one"

This reverts commit d6107f53e0.

apps/syncthing/overlays/media/deployment-patch.yaml

@@ -7,10 +7,10 @@ spec:
     containers:
       - name: syncthing
         volumeMounts:
-          # - name: sync-keys
-          #   mountPath: /var/syncthing/config/cert.pem
-          #   subPath: cert.pem
-          #   readOnly: true
+          - name: sync-keys
+            mountPath: /var/syncthing/config/cert.pem
+            subPath: cert.pem
+            readOnly: true
           - name: sync-keys
             mountPath: /var/syncthing/config/key.pem
             readOnly: true
@@ -19,3 +19,6 @@ spec:
       - name: sync-keys
         secret:
           secretName: sync-secret
+          items:
+            - key: cert.pem
+            - key: key.pem