Bump christophwurst/nextcloud_testing from 0.12.1 to 0.12.3

Bumps [christophwurst/nextcloud_testing](https://github.com/ChristophWurst/nextcloud_testing) from 0.12.1 to 0.12.3.
- [Release notes](https://github.com/ChristophWurst/nextcloud_testing/releases)
- [Commits](https://github.com/ChristophWurst/nextcloud_testing/compare/v0.12.1...v0.12.3

)

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