release: bump marketing version to 1.29.2

Version 1.29.2

release: bump marketing version to 1.29.2

- Update MARKETING_VERSION to 1.29.2 in project.yml.
- Update release note index and rename 1.29.1.html to 1.29.2.html.
- Update version references inside 1.29.2.html.
- Regenerate Xcode project with XcodeGen.

Commit: 020efb6