[3006.x] Update for deprecation of hex in pygit2 1.15.0 and above

[dmurphy18]

What does this PR do?

Updates pygit2 support to allow for removal of support for hex in pygit2 v1.15.0 and above

What issues does thihttps://github.com/saltstack/salt/issues/67017s PR fix or reference?

Fixes #67017

Previous Behavior

Errors and traceback for unsupported hex with pygit2 v1.15.0 and above

File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/utils/gitfs.py", line 2280, in find_file
    return blob, blob.hex, mode
AttributeError: '_pygit2.Blob' object has no attribute 'hex'

New Behavior

No more tracebacks and code works with pygit2 v1.15.0 and above

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

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Yes

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