Unify `Lzma` and `Xz`.

hide deprecated cask command

unpack_strategy: Move `Dmg` to above `Xz` and `Lzma`

Update Gems.

macos_requirement: fix display of versions as array

spec_helper: increase needs_network timeout and retry.

This should help with flakiness on these tests.

Mention `--greedy` when no casks were upgraded.

Fix `brew audit Formula/formula.rb`

Fix a regression introduced in PR #8542, which wouldn’t exclude
formulae and casks from stricter style checks properly unless tapped.
This caused `brew audit Formula/formula.rb` to report violations which
were not meant for formulae and casks.

The fix is to add Exclude patterns for formulae and casks in any
`git clone`d tap’s working tree.

Working outside of the productive Homebrew installation makes sure that
the latter doesn’t interfere with development, and vice versa.
It also helps track work in progress, especially if one tends to forget
things.

unlink: unlink only keg-only versioned formulae.

As otherwise we unlink those that don't conflict e.g. `gcc@8` and
`gcc@9`.

Update manpage formatting

pr-pull: skip bottles for CI-syntax-only PRs

Modify parser.rb to add a colon between each term and the line break, which `ronn` converts into a definition list.
The <br> that follows ensures each term description is on a new line in the manpage output, and also replaces the
double trailing space for generating the hard return that follows each term in the HTML output.
Also modify man.rb to print environment variables with list markup matching the cask commands, and then drop
trailing colons from both lists of terms (cask commands, env vars) and non-list terms (analytics, bundle, services;
a <br> is added here because it would prevent the term description from being indented in the manpage output).
https://docs.brew.sh/Manpage#cask-command-options-cask

pr-automerge: don't automerge PRs with linux-only label

Expand Livecheck#preprocess_url tests

docs - remove Discourse from communication methods

macOS Big Sur

build(deps-dev): bump html-proofer from 3.16.0 to 3.17.0 in /docs

Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.16.0 to 3.17.0.
- [Release notes](https://github.com/gjtorikian/html-proofer/releases)
- [Commits](https://github.com/gjtorikian/html-proofer/compare/v3.16.0...v3.17.0)
Signed-off-by: Ndependabot[bot] <support@github.com>

build(deps): bump rubocop from 1.2.0 to 1.3.0 in /Library/Homebrew