rustdoc: remove link on slice brackets

Since rust-lang#97668 was merged, the slice::get function now looks like this:

![image](https://user-images.githubusercontent.com/1593513/173430685-1dd2b275-2439-4392-b7d4-96bcb355a377.png)

That whole thing, `[T]`, is a single link to `primitive.slice.html`. This
definitely fixes it for this case, but it's not obvious what we should do for
slices of concrete types:

![image](https://user-images.githubusercontent.com/1593513/173430968-7eed1aec-b688-4f84-a492-9210aff0037a.png)

There are actually three links in that `[u8]`: the opening brace `[` is a
link to `primitive.slice.html`, the `u8` is a link to `primitive.u8.html`,
and the final `]` is a link to `primitive.slice.html`. This is a serious
[usability bug](https://usability.yale.edu/web-accessibility/articles/links):
the square braces are much too small for anyone who doesn't have perfect
motor control using mouse or touch, provide an excessive number of tab stops
for anyone using keyboard, and no visual indication whatsoever that they're
separate links.

Now that slices of generic types are linked, it seems reasonable to err on
the side of less clutter and stop linking concrete slices to the slice page.

src/librustdoc/html/format.rs

@@ -886,9 +886,9 @@ fn fmt_type<'cx>(
                 primitive_link(f, PrimitiveType::Slice, &format!("[{name}]"), cx)
             }
             _ => {
-                primitive_link(f, PrimitiveType::Slice, "[", cx)?;
+                write!(f, "[")?;
                 fmt::Display::fmt(&t.print(cx), f)?;
-                primitive_link(f, PrimitiveType::Slice, "]", cx)
+                write!(f, "]")
             }
         },
         clean::Array(ref t, ref n) => {
@@ -926,31 +926,6 @@ fn fmt_type<'cx>(
             let m = mutability.print_with_space();
             let amp = if f.alternate() { "&".to_string() } else { "&amp;".to_string() };
             match **ty {
-                clean::Slice(ref bt) => {
-                    // `BorrowedRef{ ... Slice(T) }` is `&[T]`
-                    match **bt {
-                        clean::Generic(name) => primitive_link(
-                            f,
-                            PrimitiveType::Slice,
-                            &format!("{amp}{lt}{m}[{name}]"),
-                            cx,
-                        ),
-                        _ => {
-                            primitive_link(
-                                f,
-                                PrimitiveType::Slice,
-                                &format!("{}{}{}[", amp, lt, m),
-                                cx,
-                            )?;
-                            if f.alternate() {
-                                write!(f, "{:#}", bt.print(cx))?;
-                            } else {
-                                write!(f, "{}", bt.print(cx))?;
-                            }
-                            primitive_link(f, PrimitiveType::Slice, "]", cx)
-                        }
-                    }
-                }
                 clean::DynTrait(ref bounds, ref trait_lt)
                     if bounds.len() > 1 || trait_lt.is_some() =>
                 {

src/test/rustdoc/slice-links.link_box_u32.html

@@ -1 +1 @@
-<code>pub fn gamma() -&gt; <a class="struct" href="struct.MyBox.html" title="struct foo::MyBox">MyBox</a>&lt;<a class="primitive" href="{{channel}}/core/primitive.slice.html">[</a><a class="primitive" href="{{channel}}/core/primitive.u32.html">u32</a><a class="primitive" href="{{channel}}/core/primitive.slice.html">]</a>&gt;</code>
+<code>pub fn gamma() -&gt; <a class="struct" href="struct.MyBox.html" title="struct foo::MyBox">MyBox</a>&lt;[<a class="primitive" href="{{channel}}/core/primitive.u32.html">u32</a>]&gt;</code>

src/test/rustdoc/slice-links.link_slice_generic.html

@@ -1 +1 @@
-<code>pub fn beta&lt;T&gt;() -&gt; <a class="primitive" href="{{channel}}/core/primitive.slice.html">&amp;'static [T]</a></code>
+<code>pub fn beta&lt;T&gt;() -&gt; &amp;'static <a class="primitive" href="{{channel}}/core/primitive.slice.html">[T]</a></code>

src/test/rustdoc/slice-links.link_slice_u32.html

@@ -1 +1 @@
-<code>pub fn alpha() -&gt; <a class="primitive" href="{{channel}}/core/primitive.slice.html">&amp;'static [</a><a class="primitive" href="{{channel}}/core/primitive.u32.html">u32</a><a class="primitive" href="{{channel}}/core/primitive.slice.html">]</a></code>
+<code>pub fn alpha() -&gt; &amp;'static [<a class="primitive" href="{{channel}}/core/primitive.u32.html">u32</a>]</code>