deps(worker): Update to pygit2 0.15.1

[nellh]

Resolves breaking changes from pygit2 0.14 -> 0.15.

https://github.com/libgit2/pygit2/blob/master/CHANGELOG.md#1150-2024-05-18

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 42.63%. Comparing base (80963c5) to head (b638dc7).

Files	Patch %	Lines
...rvices/datalad/datalad_service/handlers/history.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3113   +/-   ##
=======================================
  Coverage   42.63%   42.63%           
=======================================
  Files         594      594           
  Lines       37874    37874           
  Branches     1098     1098           
=======================================
  Hits        16149    16149           
  Misses      21518    21518           
  Partials      207      207           

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[effigies]

This is a deeply obnoxious refactor, as literally every object can be str()'d. I started looking into it a while back and backed off when I realized it wasn't all X.hex -> str(X). So hats off to you.

There's one line missing coverage. Are you confident in that one?

[nellh]

There's one line missing coverage. Are you confident in that one?

Added a new test to check for the expected tag reference to cover that change.