Fix cargo doc Warnings (#14948)

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As an avid `cargo doc` enjoyer I realized we had some doc warnings, so I
fixed them.

After this PR `cargo doc --workspace` should stop throwing warnings.
# User-Facing Changes
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No code changes.

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- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

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We could add a `cargo doc` CI pipeline but usually running a full `cargo
doc` takes like forever, so maybe we don't want that.

crates/nu-protocol/src/value/mod.rs

@@ -820,7 +820,7 @@ impl Value {
     /// This method is able to leverage that information encoded in a `Value` to provide more accurate
     /// type comparison than if one were to collect the type into [`Type`](crate::Type) value with [`Value::get_type`].
     ///
-    /// Empty lists are considered subtypes of all list<T> types.
+    /// Empty lists are considered subtypes of all `list<T>` types.
     ///
     /// Lists of mixed records where some column is present in all record is a subtype of `table<column>`.
     /// For example, `[{a: 1, b: 2}, {a: 1}]` is a subtype of `table<a: int>` (but not `table<a: int, b: int>`).