attr: fix expected meta-item for #[stable]

When an unexpected meta item is provided to `#[stable]`, the diagnostic
lists "since" and "note" as expected meta-items, however the surrounding
code actually expects "feature" and "since".

Signed-off-by: David Wood <david.wood@huawei.com>

compiler/rustc_attr/src/builtin.rs

@@ -404,7 +404,7 @@ where
                                         meta.span(),
                                         AttrError::UnknownMetaItem(
                                             pprust::path_to_string(&mi.path),
-                                            &["since", "note"],
+                                            &["feature", "since"],
                                         ),
                                     );
                                     continue 'outer;

src/test/ui/stability-attribute/stability-attribute-sanity-2.stderr

@@ -8,7 +8,7 @@ error[E0541]: unknown meta item 'sinse'
   --> $DIR/stability-attribute-sanity-2.rs:10:25
    |
 LL | #[stable(feature = "a", sinse = "1.0.0")]
-   |                         ^^^^^^^^^^^^^^^ expected one of `since`, `note`
+   |                         ^^^^^^^^^^^^^^^ expected one of `feature`, `since`
 
 error[E0545]: `issue` must be a non-zero numeric string or "none"
   --> $DIR/stability-attribute-sanity-2.rs:13:27

src/test/ui/stability-attribute/stability-attribute-sanity.stderr

@@ -14,7 +14,7 @@ error[E0541]: unknown meta item 'reason'
   --> $DIR/stability-attribute-sanity.rs:8:42
    |
 LL |     #[stable(feature = "a", since = "b", reason)]
-   |                                          ^^^^^^ expected one of `since`, `note`
+   |                                          ^^^^^^ expected one of `feature`, `since`
 
 error[E0539]: incorrect meta item
   --> $DIR/stability-attribute-sanity.rs:11:29