Remove publish sources

[daymxn]

Per b/377292172,

This fixes the issue with source jars not being published. Android variants are configured at configuration time, but withSourcesJar is only a function. There's no way to provide a Provider to defer setting it. Attempting to instead call it after evaluation will result in it not actually being set.

Previously, we published sources jars regardless if publishSources was set to false. Furthermore, no SDK actually had it set to false anyhow.

So moving forward, I've just removed the setting entirely- as it wasn't really being used, it fixes our issue, and reduces maintenance costs.

NO_RELEASE_CHANGE

[github-actions]

Release note changes

No release note changes were detected. If you made changes that should be
present in the next release, ensure you've added an entry in the appropriate
CHANGELOG.md file(s).

[github-actions]

Vertex AI Mock Responses Check ⚠️

A newer major version of the mock responses for Vertex AI unit tests is available. update_responses.sh should be updated to clone the latest version of the responses: v5.1

[github-actions]

buildSrc Test Results

37 tests   37 ✅  58s ⏱️
 8 suites   0 💤
 8 files     0 ❌

Results for commit 7760d3a.

[github-actions]

Test Results

 1 022 files  +   958   1 022 suites  +958   36m 24s ⏱️ + 30m 12s
 5 809 tests + 5 322   5 787 ✅ + 5 300  22 💤 +22  0 ❌ ±0 
11 703 runs  +10 723  11 659 ✅ +10 679  44 💤 +44  0 ❌ ±0 

Results for commit 7760d3a. ± Comparison against base commit d402ad0.