chore: remove outdated in-app vibration option

[naveensingh]

Type of change(s)

• [ ] Bug fix
• [x] Feature / enhancement
• [ ] Infrastructure / tooling (CI, build, deps, tests)
• [ ] Documentation

What changed and why

• Removed outdated in-app vibration preference. Rationale in https://github.com/FossifyOrg/Calendar/issues/689

Closes the following issue(s)

• Closes https://github.com/FossifyOrg/Calendar/issues/689

Checklist

• [x] I read the contribution guidelines.
• [ ] I manually tested my changes on device/emulator (if applicable).
• [ ] I updated the "Unreleased" section in CHANGELOG.md (if applicable).
• [ ] All checks are passing.