chore(deps): pin nginx docker tag (sourcegraph#185)

Author: renovate[bot]

configure/nginx-svc/nginx.Deployment.yaml

@@ -16,7 +16,7 @@ spec:
     spec:
       containers:
       - name: nginx
-        image: nginx:1.7.9
+        image: nginx:1.7.9@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
         volumeMounts:
         - name: nginx-config
           mountPath: /etc/nginx