Log Message:
devel/difftastic: update to 0.51.1

v0.51.1
This is the same code as 0.51.0, but fixes a CI issue so that prebuilt binaries
are attached.

Parsing
 - Updated Bash, Python and Rust parsers.

Display
 - Added a JSON display option. This is currently unstable, and requires you to
   set DFT_UNSTABLE. The JSON structure may change in future.
 - Please give it a try and give feedback on GitHub issues.

Build
 - Added support for Linux with musl, Linux on aarch64, and macOS on aarch64.

Note that Difftastic already worked on these platforms, but they are now tested
in CI and will be included in prebuilt binaries in releases.