Brew: 2.7.4 Release

Release notes for major and minor releases can be found in the Homebrew blog. - utils/git_repository: use Pathname.pwd if no repo specified (@SeekingMeaning) - completions: make opt-in only (@Rylan12) - Keg: allow overwriting same-formula conflicts (@mistydemeo) - Popen spec: ensure Rubocop is happy (@Homebrew) - Cask tests: temporarily disable broken test (@mistydemeo) - utils/popen: add safe argument to popen_read and popen_write (@SeekingMeaning) - shims/super/cc: fix most style errors (@SeekingMeaning) - Livecheck: Skip archived stable URLs in formulae (@samford) - build(deps): bump tapioca from 0.4.10 to 0.4.11 in /Library/Homebrew (@Homebrew) - Ignore invalid keys when reading existing Cask::Config. (@reitermarkus) - rubocops: migrate to rubocop v1 API (@jonchang) - build(deps): bump sorbet from 0.5.6205 to 0.5.6206 in /Library/Homebrew (@Homebrew) - Improve audit for livecheck in casks. (@reitermarkus) - utils/ast: move helper functions from FormulaAST to AST (@SeekingMeaning) - test/utils/*: use described_class or named subject (@SeekingMeaning) - upgrade: show formula caveats after casks have been updated (@SeekingMeaning) - build(deps): bump rubocop from 1.8.0 to 1.8.1 in /Library/Homebrew (@Homebrew) - sorbet: Update RBI files. (@Homebrew) - docs: add brew livecheck documentation (@samford) - Improve documentation and add type signatures. (@jonchang) - Only select Sparkle items for macOS. (@reitermarkus) - utils/github: cleanup (@SeekingMeaning) - bump-formula-pr: cleanup (@SeekingMeaning) - utils/ast: add FormulaAST class (@SeekingMeaning) - bump-*-pr: check existing PRs for exact file match (@SeekingMeaning)