Remove must_use from ALLOWED_ATTRIBUTES

This is a fairly common attribute on methods, but is not something you
need to know when reading the method docs - the purpose of the attribute
is for the compiler to tell you about it if you forget to use a value.

Removing reclaims some valuable space in the summary of methods.

src/librustdoc/html/render/mod.rs

@@ -965,14 +965,8 @@ fn method(
     }
 }
 
-const ALLOWED_ATTRIBUTES: &[Symbol] = &[
-    sym::export_name,
-    sym::link_section,
-    sym::must_use,
-    sym::no_mangle,
-    sym::repr,
-    sym::non_exhaustive,
-];
+const ALLOWED_ATTRIBUTES: &[Symbol] =
+    &[sym::export_name, sym::link_section, sym::no_mangle, sym::repr, sym::non_exhaustive];
 
 fn attributes(it: &clean::Item) -> Vec<String> {
     it.attrs

src/test/rustdoc/attributes.rs

@@ -8,14 +8,6 @@ pub extern "C" fn f() {}
 #[export_name = "bar"]
 pub extern "C" fn g() {}
 
-// @matches foo/enum.Foo.html '//*[@class="rust enum"]' \
-//      '#\[repr\(i64\)\]\n#\[must_use\]'
-#[repr(i64)]
-#[must_use]
-pub enum Foo {
-    Bar,
-}
-
 // @has foo/struct.Repr.html '//*[@class="docblock type-decl"]' '#[repr(C, align(8))]'
 #[repr(C, align(8))]
 pub struct Repr;

src/test/rustdoc/cap-lints.rs

@@ -3,8 +3,7 @@
 // therefore should not concern itself with the lints.
 #[deny(warnings)]
 
-// @has cap_lints/struct.Foo.html //pre '#[must_use]'
-#[must_use]
+// @has cap_lints/struct.Foo.html //* 'Struct Foo'
 pub struct Foo {
     field: i32,
 }

src/test/rustdoc/must-use.rs

-// @has must_use/struct.Struct.html //pre '#[must_use]'
-#[must_use]
-pub struct Struct {
-    field: i32,
-}
-
-// @has must_use/enum.Enum.html //pre '#[must_use = "message"]'
-#[must_use = "message"]
-pub enum Enum {
-    Variant(i32),
-}

src/test/rustdoc/trait-attributes.rs

-#![crate_name = "foo"]
-
-
-pub trait Foo {
-    // @has foo/trait.Foo.html '//div[@id="tymethod.foo"]//div[@class="code-attribute"]' '#[must_use]'
-    #[must_use]
-    fn foo();
-}
-
-#[must_use]
-pub struct Bar;
-
-impl Bar {
-    // @has foo/struct.Bar.html '//div[@id="method.bar"]//div[@class="code-attribute"]' '#[must_use]'
-    #[must_use]
-    pub fn bar() {}
-
-    // @has foo/struct.Bar.html '//div[@id="method.bar2"]//div[@class="code-attribute"]' '#[must_use]'
-    #[must_use]
-    pub fn bar2() {}
-}