CloneUrlInput: All it to expand vertically

Ideally one should remove the code duplication of this form, but for now
duplicating the code is just so much simpler.

lib/screens/githostsetup_clone_url.dart

@@ -54,6 +54,8 @@ class GitCloneUrlPageState extends State<GitCloneUrlPage> {
         textInputAction: TextInputAction.done,
         onFieldSubmitted: (String _) => formSubmitted(),
         initialValue: widget.initialValue,
+        minLines: 1,
+        maxLines: 3,
       ),
     );