Mention unnameable_types in unreachable_pub documentation.

This link makes sense because someone who wishes to avoid unusable `pub`
is likely, but not guaranteed, to be interested in avoiding unnameable
types.

Also fixed some grammar problems I noticed in the area.

Fixes #116604.

compiler/rustc_lint/src/builtin.rs

@@ -1244,8 +1244,8 @@ fn check_fn(
 
 declare_lint! {
     /// The `unreachable_pub` lint triggers for `pub` items not reachable from other crates - that
-    /// means neither directly accessible, nor reexported, nor leaked through things like return
-    /// types.
+    /// means neither directly accessible, nor reexported (with `pub use`), nor leaked through
+    /// things like return types (which the [`unnameable_types`] lint can detect if desired).
     ///
     /// ### Example
     ///
@@ -1272,8 +1272,10 @@ fn check_fn(
     /// intent that the item is only visible within its own crate.
     ///
     /// This lint is "allow" by default because it will trigger for a large
-    /// amount existing Rust code, and has some false-positives. Eventually it
+    /// amount of existing Rust code, and has some false-positives. Eventually it
     /// is desired for this to become warn-by-default.
+    ///
+    /// [`unnameable_types`]: #unnameable-types
     pub UNREACHABLE_PUB,
     Allow,
     "`pub` items not reachable from crate root"

compiler/rustc_lint_defs/src/builtin.rs

@@ -4362,7 +4362,7 @@
     /// ### Explanation
     ///
     /// It is often expected that if you can obtain an object of type `T`, then
-    /// you can name the type `T` as well, this lint attempts to enforce this rule.
+    /// you can name the type `T` as well; this lint attempts to enforce this rule.
     /// The recommended action is to either reexport the type properly to make it nameable,
     /// or document that users are not supposed to be able to name it for one reason or another.
     ///