Update google/cloud-tools requirement from ^0.14.0 to ^0.15.0

Updates the requirements on [google/cloud-tools](https://github.com/GoogleCloudPlatform/php-tools) to permit the latest version.
- [Release notes](https://github.com/GoogleCloudPlatform/php-tools/releases)
- [Commits](GoogleCloudPlatform/php-tools@v0.14.0...v0.15.0)

---
updated-dependencies:
- dependency-name: google/cloud-tools
  dependency-type: direct:development
...

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

composer.json

@@ -46,7 +46,7 @@
     "guzzlehttp/psr7": "^2.7.0"
   },
   "require-dev": {
-    "google/cloud-tools": "^0.14.0",
+    "google/cloud-tools": "^0.15.0",
     "jetbrains/phpstorm-attributes": "^1.1",
     "phpunit/php-code-coverage": "^9.2.31",
     "phpunit/phpunit": "^9.6.20"