servo: Merge #5733 - Remove unnecessary clone in Document constructor (from marcusklaas:issue-5719); r=Manishearth

This closes issue https://github.com/servo/servo/issues/5719.

Source-Repo: https://github.com/servo/servo
Source-Revision: c3ed0fd57377c617ef877cd685d3248ce37d1710

servo/components/script/dom/document.rs

@@ -794,7 +794,7 @@ impl Document {
             implementation: Default::default(),
             location: Default::default(),
             content_type: match content_type {
-                Some(string) => string.clone(),
+                Some(string) => string,
                 None => match is_html_document {
                     // https://dom.spec.whatwg.org/#dom-domimplementation-createhtmldocument
                     IsHTMLDocument::HTMLDocument => "text/html".to_owned(),