Fix Url::into_string deprecation warning

`url::Url::into_string` is deprecated. The `Into<String>` implementation
is now used.

Signed-off-by: Paul Mabileau <paulmabileau@hotmail.fr>

Author: PaulDance

crates/cargo-test-support/src/registry.rs

@@ -178,12 +178,7 @@ impl RegistryBuilder {
         }
 
         if self.replace_crates_io {
-            init_registry(
-                registry_path(),
-                dl_url().into_string(),
-                api_url(),
-                api_path(),
-            );
+            init_registry(registry_path(), dl_url().into(), api_url(), api_path());
         }
 
         if self.alternative {

crates/mdman/src/lib.rs

@@ -96,7 +96,7 @@ fn join_url<'a>(base: Option<&Url>, dest: CowStr<'a>) -> CowStr<'a> {
                 let joined = base_url.join(&dest).unwrap_or_else(|e| {
                     panic!("failed to join URL `{}` to `{}`: {}", dest, base_url, e)
                 });
-                joined.into_string().into()
+                String::from(joined).into()
             }
         }
         None => dest,