Bump rollup in /XperienceByKentico/PartialWidgetPage.Xperience.Mvc.Core

Bumps [rollup](https://github.com/rollup/rollup) from 4.21.0 to 4.28.1.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](rollup/rollup@v4.21.0...v4.28.1)

---
updated-dependencies:
- dependency-name: rollup
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]