chore: fix doc url (#280)

It has to end with version (or latest).
Fixes ecb7374.

Author: stoeckmann

src/lib.rs

@@ -160,7 +160,7 @@
 #![doc(
     html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
     html_favicon_url = "https://www.rust-lang.org/favicon.ico",
-    html_root_url = "https://docs.rs/tempfile/latest/tempfile"
+    html_root_url = "https://docs.rs/tempfile/latest"
 )]
 #![cfg_attr(test, deny(warnings))]
 #![deny(rust_2018_idioms)]