chore: release 3.9.1 (#290)

🤖 I have created a release \*beep\* \*boop\*
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### [3.9.1](https://www.github.com/googleapis/nodejs-secret-manager/compare/v3.9.0...v3.9.1) (2021-08-17)


### Bug Fixes

* **deps:** google-gax v2.24.1 ([#289](https://www.github.com/googleapis/nodejs-secret-manager/issues/289)) ([e802581](https://www.github.com/googleapis/nodejs-secret-manager/commit/e802581bf44ce6175cefdd13e8aeb6e107cb0cd2))
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This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).

secret-manager/package.json

@@ -14,7 +14,7 @@
     "test": "c8 mocha --recursive test/ --timeout=800000"
   },
   "dependencies": {
-    "@google-cloud/secret-manager": "^3.9.0"
+    "@google-cloud/secret-manager": "^3.9.1"
   },
   "devDependencies": {
     "c8": "^7.0.0",