Use Erlang 27 in CI for tests

[Zerpet]

Proposed Changes

Run tests with Erlang 27. Erlang 27 is fully supported in main and v4.1.x. Erlang 27 is already used for build and XREF.

Types of Changes

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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Checklist

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Further Comments

Erlang 27 is fully supported in main and v4.1.x. Support for Erlang 26
in v4.1 remains. It's better to "drop" erlang 26 from CI because, at the
moment, our PRs and commits to main trigger about 270 jobs. If we just
add '27' to the matrix, we would spawn ~216 more jobs, totalling around
496 jobs per PR and commit to main. That's simply too much, because it's
reaching the usage limits of Github Actions [1], namely the 256 limit of
matrix jobs.

[1]
https://docs.github.com/en/actions/administering-github-actions/usage-limits-billing-and-administration#usage-limits

[michaelklishin]

FTR, Erlang 27 is fully supported in 4.0.x, too. No objections to switching to 27.3 from me, though.