deps: bump ethers from 6.13.3 to 6.13.4

Bumps [ethers](https://github.com/ethers-io/ethers.js) from 6.13.3 to 6.13.4.
- [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@v6.13.3...v6.13.4)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

observer/package.json

@@ -19,7 +19,7 @@
     "@filecoin-station/spark-stats-db": "^1.0.0",
     "@sentry/node": "^8.34.0",
     "debug": "^4.3.7",
-    "ethers": "^6.13.3",
+    "ethers": "^6.13.4",
     "pg": "^8.13.0"
   },
   "standard": {