Bump dotenv from 8.6.0 to 16.3.1 in /examples/ethers-signer

Bumps [dotenv](https://github.com/motdotla/dotenv) from 8.6.0 to 16.3.1.
- [Changelog](https://github.com/motdotla/dotenv/blob/master/CHANGELOG.md)
- [Commits](motdotla/dotenv@v8.6.0...v16.3.1)

---
updated-dependencies:
- dependency-name: dotenv
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

examples/ethers-signer/package.json

@@ -7,7 +7,7 @@
   "license": "MIT",
   "dependencies": {
     "@openzeppelin/defender-relay-client": "1.49.0-rc.0",
-    "dotenv": "^8.2.0",
+    "dotenv": "^16.3.1",
     "ethers": "^5.7.2"
   }
 }