Brew: 4.2.21 Release

<!-- Release notes generated using configuration in .github/release.yml at master -->

What's Changed

• Document Tab.for_keg and use Keg#tab where possible. by @reitermarkus in https://github.com/Homebrew/brew/pull/17168
• shims/super/cc: avoid passing -oso_prefix during configure by @carlocab in https://github.com/Homebrew/brew/pull/17169
• startup/bootsnap: raise repeated LoadError. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17177
• fix: Display a warning (instead of exiting early) when unable to find recent issues on a tap by @boblail in https://github.com/Homebrew/brew/pull/17182
• brew.sh: auto-update 3rd-party taps more often. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17179
• Cookbook document what Operation not permitted means by @mohawk2 in https://github.com/Homebrew/brew/pull/17176
• install-bundler-gems: change_privilege when necessary. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17178
• Remove disabled extend. by @reitermarkus in https://github.com/Homebrew/brew/pull/17184
• Various improvements for brew command by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17186
• Call Homebrew.install_bundler_gems! more consistently. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17185
• Optimise more command handling/speed by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17188
• Remove the signing workflow for backfill attestation checks by @josephsweeney in https://github.com/Homebrew/brew/pull/17190
• brew.sh: fix argument handling for a few commands. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17192
• New formula internal json v3 dependencies format by @apainintheneck in https://github.com/Homebrew/brew/pull/17153
• Warn about undocumented non-private APIs. by @reitermarkus in https://github.com/Homebrew/brew/pull/17165
• cmd/leaves: fix an undefined method error by @ZhongRuoyu in https://github.com/Homebrew/brew/pull/17200
• Fix internal formula json v3 frozen hash parsing bug by @apainintheneck in https://github.com/Homebrew/brew/pull/17201
• compilers: add gcc-14 by @fxcoudert in https://github.com/Homebrew/brew/pull/17202
• Library/Homebrew: move stdin ruby scripts to files under utils. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17204
• homebrew/cask-versions: remove by @razvanazamfirei in https://github.com/Homebrew/brew/pull/17207
• docs: update for Homebrew/cask-versions deprecation by @p-linnane in https://github.com/Homebrew/brew/pull/17208
• Cask-Cookbook: remove outdated URL by @p-linnane in https://github.com/Homebrew/brew/pull/17210
• various: remove remaining Homebrew/cask-versions references by @p-linnane in https://github.com/Homebrew/brew/pull/17209
• formula: fix missing test resources. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/17211
• dev-cmd/tests: skip tests that require core if it's not tapped by @apainintheneck in https://github.com/Homebrew/brew/pull/17212
• docs/cask-cookbook: token examples for versioned/development casks by @bevanjkay in https://github.com/Homebrew/brew/pull/17214
• Pypi: Update strategy regex by @samford in https://github.com/Homebrew/brew/pull/17218
• cmd/generate-cask-api: include cask renames by @EricFromCanada in https://github.com/Homebrew/brew/pull/17225
• tap: tweak core tap warning by @apainintheneck in https://github.com/Homebrew/brew/pull/17227
• attestations: improve authentication techniques by @woodruffw in https://github.com/Homebrew/brew/pull/17220
• Add resource signature. by @reitermarkus in https://github.com/Homebrew/brew/pull/17223
• Replace FormulaTextAuditor usage by @issyl0 in https://github.com/Homebrew/brew/pull/17228

New Contributors

• @mohawk2 made their first contribution in https://github.com/Homebrew/brew/pull/17176

Full Changelog: https://github.com/Homebrew/brew/compare/4.2.20...4.2.21