Don't bring up authorization just because group ID doesn't match

[zorgiepoo]

Don't bring up authorization just because group ID doesn't match

Let us not bother the user in the more unusual case the group can't be changed. I think this is the right thing to do for most apps.. Apps that want auth should be owned by root user, Sparkle tools like BinaryDelta also don't support weird permission modes like 0770 last I recall.

This change is not back-portable to 1.x (see below).

Fixes #1108

Checklist:

• My change is being tested and reviewed against the Sparkle 2.x branch. New changes must be developed on the 2.x development branch first.
• My change is being backported to master branch (Sparkle 1.x). Please create a separate pull request for 1.x, should it be backported. Note 1.x is feature frozen and is only taking bug fixes, localization updates, and critical OS adoption enhancements - No, more work is required to do this properly in 1.x to ensure group is still changed when auth will otherwise be needed for moving the apps, which may be risky / difficult and I don't want to do the testing & refactoring work there. Also not critical enough of an issue to back port considering how long it's been around and few developers noticed.
• I have reviewed and commented my code, particularly in hard-to-understand areas.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• My change is or requires a documentation or localization update

Testing

I tested and verified my change by using one or multiple of these methods:

• Sparkle Test App
• Unit Tests
• My own app
• Other (please specify)

With Sparkle Test App, tested:
Regular app update with user:staff (no auth)
App update that is root:wheel (auth)
App update that is user:wheel (no auth)
App update whose parent directory is root:wheel (auth)

macOS version tested: 11.2.3 (20D91)