Keeps exec probe.

This is to make sure nginx does cache results from a well started php process.

nextcloud/manifests/app.yml

@@ -182,12 +182,9 @@ spec:
             - name: Host
               value: localhost
         readinessProbe:
-          httpGet:
-            path: /heartbeat
-            port: 80
-            httpHeaders:
-            - name: Host
-              value: localhost
+          exec:
+            command:
+            - /php-fpm-healthcheck
         ports:
         - containerPort: 9000
           name: api