Update Prometheus port name per comments

gitlab/prometheus-deployment.yml

@@ -16,7 +16,7 @@ spec:
         args:
           - '-config.file=/prometheus-data/prometheus.yml'
         ports:
-        - name: gitlab-prom
+        - name: prometheus
           containerPort: 9090
         volumeMounts:
         - name: data-volume

gitlab/prometheus-svc.yml

@@ -9,7 +9,7 @@ spec:
   selector:
     app: gitlab-prometheus
   ports:
-  - name: gitlab-prom
+  - name: prometheus
     protocol: TCP
     port: 9090
-    targetPort: gitlab-prom
+    targetPort: prometheus