chore: release 0.31.1 (#721)

Author: yoshi-automation

handwritten/pubsub/samples/package.json

@@ -14,7 +14,7 @@
     "test": "mocha system-test --timeout 600000"
   },
   "dependencies": {
-    "@google-cloud/pubsub": "^0.31.0",
+    "@google-cloud/pubsub": "^0.31.1",
     "yargs": "^14.0.0"
   },
   "devDependencies": {