Fix warning: varbase_auth.install includes the removed includes/helpers.inc

Problem/Motivation

On 9.2.x, installing varbase_auth logs:

include_once(.../varbase_auth/includes/helpers.inc): Failed to open stream: No such file or directory varbase_auth.install:12

The helpers were moved into the OOP hook class on 9.2.x and includes/helpers.inc was removed, but varbase_auth.install still includes it.

Steps to reproduce

1. Install Varbase 9.2.x with the Social authentications component (or drush pm:enable varbase_auth).
2. The two include_once warnings appear.

Proposed resolution

Drop the includes/helpers.inc include from varbase_auth.install (keep includes/updates.inc).

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

• fix: #3608534 Drop the removed includes/helpers.inc include from varbase_auth.install