build(deps-dev): bump titanium-docgen from 4.7.0 to 4.8.1
build(deps-dev): bump titanium-docgen from 4.7.0 to 4.8.1

Bumps [titanium-docgen](https://github.com/appcelerator/docs-devkit/tree/HEAD/packages/titanium-docgen) from 4.7.0 to 4.8.1.
- [Release notes](https://github.com/appcelerator/docs-devkit/releases)
- [Changelog](https://github.com/appcelerator/docs-devkit/blob/develop/packages/titanium-docgen/CHANGELOG.md)
- [Commits](https://github.com/appcelerator/docs-devkit/commits/v4.8.1/packages/titanium-docgen)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
appcelerator-modules/ti.imagefactory,appcelerator-modules/ti.imagefactory,appcelerator-modules/ti.imagefactory