Drop social_auth_twitter references (removed in the 9.2.x Drupal 11 line)

Problem/Motivation

Varbase 9.2.x drops drupal/social_auth_twitter (X/Twitter API removal), but the module's README.md still lists a Social Auth Twitter bullet among the dependencies, which is stale on the 9.2.x branch since the module no longer depends on it.

Steps to reproduce

View README.md on the 9.2.x branch and compare it with composer.json/varbase_auth.info.yml.

Proposed resolution

Remove the single leftover * [Social Auth Twitter](https://www.drupal.org/project/social_auth_twitter). bullet from README.md.

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Reviewed by a human
• ✅ Code review by maintainers
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes
• ✅ Release varbase-9.2.0, varbase_auth-9.2.0

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• task: #3608749 Drop social_auth_twitter references removed in 9.2.x