Rollup merge of rust-lang#119866 - smoelius:patch-2, r=compiler-errors

Convert `effects` description to doc comment

So that it is visible here: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_feature/unstable/struct.Features.html#structfield.effects

r? `@fee1-dead`

Author: matthiaskrgr

compiler/rustc_feature/src/unstable.rs

@@ -450,7 +450,7 @@ declare_features! (
     (unstable, doc_masked, "1.21.0", Some(44027)),
     /// Allows `dyn* Trait` objects.
     (incomplete, dyn_star, "1.65.0", Some(102425)),
-    // Uses generic effect parameters for ~const bounds
+    /// Uses generic effect parameters for ~const bounds
     (unstable, effects, "1.72.0", Some(102090)),
     /// Allows `X..Y` patterns.
     (unstable, exclusive_range_pattern, "1.11.0", Some(37854)),