Fix clippy warnings

Fix linter warning from clippy about unnecessary borrows - "This expression borrows a reference ... that is immediately dereferenced by the compiler"

src/testserver.rs

@@ -85,7 +85,7 @@ impl TestHeaders {
         if self.0.is_empty() {
             ""
         } else {
-            &self.0[0].split(' ').nth(1).unwrap()
+            self.0[0].split(' ').nth(1).unwrap()
         }
     }