Bump ethers from 5.7.2 to 6.9.0 in /examples/keeper-network

Bumps [ethers](https://github.com/ethers-io/ethers.js) from 5.7.2 to 6.9.0.
- [Release notes](https://github.com/ethers-io/ethers.js/releases)
- [Changelog](https://github.com/ethers-io/ethers.js/blob/main/CHANGELOG.md)
- [Commits](ethers-io/ethers.js@v5.7.2...v6.9.0)

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

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

examples/keeper-network/package.json

@@ -7,6 +7,6 @@
   "dependencies": {
     "@openzeppelin/defender-relay-client": "1.53.0-rc.0",
     "dotenv": "^8.2.0",
-    "ethers": "^5.7.2"
+    "ethers": "^6.9.0"
   }
 }