test(updater): Accept either main or master as sentry-cli main branch

[vaind]

Summary

The Updater @ {ubuntu,macos,windows} jobs in Script Tests have been failing on main since #165 was merged (failing run):

Expected 'mainBranch=main' to be found in collection
@('originalTag=0', 'latestTag=0.28.0', 'latestTagNice=v0.28.0',
  'url=https://github.com/getsentry/sentry-cli', 'mainBranch=master'),
but it was not found.

Why it didn't fail on the PR

The test asserts against the live state of getsentry/sentry-cli via git ls-remote. At PR time (2026-05-07), both main and master of sentry-cli pointed at the same HEAD commit, so the SHA filter matched both refs and the new Select-Object -First 1 returned main (alphabetically first). At post-merge time (2026-05-11), sentry-cli's main and master no longer share a SHA — only master matches HEAD — so the script now emits mainBranch=master.

HEAD                660e98b...   (same as master)
refs/heads/main     54eefbd...   (different)
refs/heads/master   660e98b...

Fix

Accept either mainBranch=main or mainBranch=master rather than baking transient upstream branch state into the assertion.

Test plan

• All 34 Pester tests pass locally on macOS (Invoke-Pester on update-dependency.Tests.ps1)
• Script Tests pass in CI on Ubuntu, macOS, Windows

[github-actions]

	Warnings
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