Auto merge of #7827 - zvavybir:master, r=xFrednet

Fixed naive doc formatting for `#[must_use]` lints

The documentation of a few lints around the `#[must_use]` attribute had a few times "[`#[must_use]`]" (without the parentheses, but with the `[]`) and once the "`" was missing.

changelog: Fixed naive doc formatting for `#[must_use]` lints ([`must_use_unit`], [`double_must_use`], [`must_use_candidate`], [`let_underscore_must_use`])