Fix broken intra-doc link to DiagCtxtHandle::err_count

Author: xmakro

compiler/rustc_errors/src/lib.rs

@@ -729,7 +729,7 @@ impl<'a> DiagCtxtHandle<'a> {
 
     /// The number of errors that have been emitted on the *current thread*.
     ///
-    /// Unlike [`DiagCtxt::err_count`], which counts errors emitted by all
+    /// Unlike [`DiagCtxtHandle::err_count`], which counts errors emitted by all
     /// threads, this only counts errors emitted by the calling thread. It is
     /// meant for code that takes a before/after delta to detect whether a unit
     /// of work emitted an error, and must not be misled by errors emitted on