Rollup merge of #74912 - giraffate:fix_broken_link_in_unstable_plugin…

…_book, r=jonas-schievink

Fix broken link in unstable book `plugin`

There is broken link in https://doc.rust-lang.org/unstable-book/language-features/plugin.html#lint-plugins.

src/doc/unstable-book/src/language-features/plugin.md

@@ -35,7 +35,7 @@ of a library.
 Plugins can extend [Rust's lint
 infrastructure](../../reference/attributes/diagnostics.md#lint-check-attributes) with
 additional checks for code style, safety, etc. Now let's write a plugin
-[`lint_plugin_test.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui-fulldeps/auxiliary/lint_plugin_test.rs)
+[`lint-plugin-test.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs)
 that warns about any item named `lintme`.
 
 ```rust,ignore