specify a prim@slice in docs

i am not quite sure how this failure is in any way related to this pr,
since i am only touching inherent functions on str? but sure.

Author: m4rch3n1ng

library/core/src/str/mod.rs

@@ -169,7 +169,7 @@ impl str {
     /// UTF-8, and then does the conversion.
     ///
     /// [`&str`]: str
-    /// [byteslice]: slice
+    /// [byteslice]: prim@slice
     ///
     /// If you are sure that the byte slice is valid UTF-8, and you don't want to
     /// incur the overhead of the validity check, there is an unsafe version of