fix: register igamma

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes are missing coverage. Please review.

:exclamation: No coverage uploaded for pull request base (main@169a9e5). Click here to learn what that means.

Files	Patch %	Lines
src/unxt/_quantity/register_primitives.py	60.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #101 +/- ## ======================================= Coverage ? 88.95% ======================================= Files ? 19 Lines ? 1240 Branches ? 0 ======================================= Hits ? 1103 Misses ? 137 Partials ? 0 ```

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