chore: bump @openzeppelin/defender-sdk-base-client in /packages/proposal

Bumps [@openzeppelin/defender-sdk-base-client](https://github.com/OpenZeppelin/defender-sdk) from 1.15.2 to 2.7.0.
- [Release notes](https://github.com/OpenZeppelin/defender-sdk/releases)
- [Commits](https://github.com/OpenZeppelin/defender-sdk/compare/@openzeppelin/defender-sdk-base-client@1.15.2...@openzeppelin/defender-sdk-base-client@2.7.0)

---
updated-dependencies:
- dependency-name: "@openzeppelin/defender-sdk-base-client"
  dependency-version: 2.7.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

packages/proposal/package.json

@@ -20,7 +20,7 @@
   "author": "OpenZeppelin Defender <defender@openzeppelin.com>",
   "license": "MIT",
   "dependencies": {
-    "@openzeppelin/defender-sdk-base-client": "^1.15.0",
+    "@openzeppelin/defender-sdk-base-client": "^2.7.0",
     "axios": "^1.7.2",
     "ethers": "^6.9.0",
     "lodash": "^4.17.21"