Fix URL encoding of % sign in Rust Doc.

src/librustdoc/html/render/mod.rs

@@ -1940,8 +1940,6 @@ fn dont_escape(c: u8) -> bool {
             // While the same is not true for hashes, rustdoc only needs to be
             // consistent with itself when encoding them.
             st += "+";
-        } else if b == b'%' {
-            st += "%%";
         } else {
             write!(st, "%{:02X}", b).unwrap();
         }