build(deps): bump google-genai from 1.71.0 to 1.73.0

Bumps [google-genai](https://github.com/googleapis/python-genai) from 1.71.0 to 1.73.0.
- [Release notes](https://github.com/googleapis/python-genai/releases)
- [Changelog](https://github.com/googleapis/python-genai/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-genai@v1.71.0...v1.73.0)

---
updated-dependencies:
- dependency-name: google-genai
  dependency-version: 1.73.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -13,7 +13,7 @@ google-api-core==2.30.2
 google-api-python-client==2.193.0
 google-auth==2.49.1
 google-auth-httplib2==0.3.1
-google-genai==1.71.0
+google-genai==1.73.0
 googleapis-common-protos==1.74.0
 grpcio==1.80.0
 grpcio-status==1.71.2