Change a typo mistake in the-doc-attribute.md

I guess that `Bar` in the section I changed should be `bar` because when I run the program it has its page under struct but bar doesn't have any page.

src/doc/rustdoc/src/write-documentation/the-doc-attribute.md

@@ -201,7 +201,7 @@ mod bar {
 # fn main() {}
 ```
 
-Here, because `bar` is not public, `Bar` wouldn't have its own page, so there's nowhere
+Here, because `bar` is not public, `bar` wouldn't have its own page, so there's nowhere
 to link to. `rustdoc` will inline these definitions, and so we end up in the same case
 as the `#[doc(inline)]` above; `Bar` is in a `Structs` section, as if it were defined at
 the top level. If we add the `no_inline` form of the attribute: