Don't mark associated items as traits

This caused the following false positive:

```
warning: unresolved link to `Default::default`
 --> /home/joshua/rustc2/default.rs:1:14
  |
1 | /// Link to [Default::default()]
  |              ^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default
note: this item resolved to a trait, which did not match the disambiguator 'fn'
 --> /home/joshua/rustc2/default.rs:1:14
  |
1 | /// Link to [Default::default()]
  |              ^^^^^^^^^^^^^^^^^^
```

1 files changed, 3 insertions, 0 deletions

diff --git a/src/test/rustdoc/intra-link-trait-item.rs b/src/test/rustdoc/intra-link-trait-item.rs
new file mode 100644
index 00000000000..70d36358fc2
--- /dev/null
+++ b/src/test/rustdoc/intra-link-trait-item.rs
@@ -0,0 +1,3 @@
+#![deny(broken_intra_doc_links_)]
+/// Link to [Default::default()]
+pub fn f() {}