ci(macos): automatically determine default branch for homebrew formula

[ReenigneArcher]

Description

PRs with a default branch other than nightly would fail the audit of the homebrew formula. This PR modifies the behavior so the default branch is determined automatically.

Screenshot

Issues Fixed or Closed

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)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 6.10%. Comparing base (526121d) to head (8222fba).

Additional details and impacted files

@@           Coverage Diff           @@
##           nightly   #2317   +/-   ##
=======================================
  Coverage     6.09%   6.10%           
=======================================
  Files           86      86           
  Lines        18518   18518           
  Branches      8404    8404           
=======================================
+ Hits          1129    1130    +1     
- Misses       15558   15559    +1     
+ Partials      1831    1829    -2     

Flag	Coverage Δ
Linux	4.11% <ø> (ø)
Windows	1.57% <ø> (ø)
macOS-12	8.23% <ø> (+0.12%)	⬆️
macOS-13	7.44% <ø> (ø)
macOS-14	7.72% <ø> (ø)

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see 3 files with indirect coverage changes