chore(deps): bump the pip group across 3 directories with 2 updates

Bumps the pip group with 1 update in the /contributing/samples/adk_knowledge_agent directory: [google-adk](https://github.com/google/adk-python).
Bumps the pip group with 2 updates in the /contributing/samples/authn-adk-all-in-one directory: [google-adk](https://github.com/google/adk-python) and [requests](https://github.com/psf/requests).
Bumps the pip group with 1 update in the /contributing/samples/authn-adk-all-in-one/adk_agents directory: [google-adk](https://github.com/google/adk-python).


Updates `google-adk` from 1.15.1 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.15.1 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.15.1 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `requests` from 2.32.4 to 2.33.0
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/main/HISTORY.md)
- [Commits](psf/requests@v2.32.4...v2.33.0)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

Updates `google-adk` from 1.12 to 1.28.1
- [Release notes](https://github.com/google/adk-python/releases)
- [Changelog](https://github.com/google/adk-python/blob/main/CHANGELOG.md)
- [Commits](v1.15.1...v1.28.1)

---
updated-dependencies:
- dependency-name: google-adk
  dependency-version: 1.28.1
  dependency-type: direct:production
- dependency-name: google-adk
  dependency-version: 1.28.1
  dependency-type: direct:production
- dependency-name: google-adk
  dependency-version: 1.28.1
  dependency-type: direct:production
- dependency-name: requests
  dependency-version: 2.33.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

contributing/samples/adk_knowledge_agent/requirements.txt

@@ -1 +1 @@
-google-adk[a2a]==1.15.1
+google-adk[a2a]==1.28.1

contributing/samples/authn-adk-all-in-one/adk_agents/requirements.txt

@@ -1 +1 @@
-google-adk==1.12
+google-adk==1.28.1

contributing/samples/authn-adk-all-in-one/requirements.txt

@@ -1,6 +1,6 @@
-google-adk==1.12
+google-adk==1.28.1
 Flask==3.1.3
 flask-cors==6.0.1
 python-dotenv==1.1.1
 PyJWT[crypto]==2.10.1
-requests==2.32.4
+requests==2.33.0