Bump gradle-release from 2.6.0 to 2.8.1
Bump gradle-release from 2.6.0 to 2.8.1

Bumps [gradle-release](https://github.com/researchgate/gradle-release) from 2.6.0 to 2.8.1.
- [Release notes](https://github.com/researchgate/gradle-release/releases)
- [Changelog](https://github.com/researchgate/gradle-release/blob/master/CHANGELOG.md)
- [Commits](https://github.com/researchgate/gradle-release/compare/2.6.0...2.8.1)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
sirixdb/sirix,sirixdb/sirix,sirixdb/sirix,sirixdb/sirix