testing/cargo-crev: upgrade to 0.25.6
Changelog is missing from upstream since 0.23.0. Commit messages are also missing, but it seems like a very minor update,
https://github.com/crev-dev/cargo-crev/compare/v0.25.5...v0.25.6
Signed-off-by: Thomas Böhler witcher@wiredspace.de