code: Do not show selected branch for a commit

It was incorrect and is not necessary.

I think in future we can show the branches and tags which contain the
commit, instead of the selected branch.

app/views/code/diff.scala.html

@@ -36,17 +36,6 @@
 <div class="page-wrap-outer">
     <div class="project-page-wrap">
         <div id="code-browse-wrap" class="code-browse-wrap">
-            <select id="branches" data-toggle="select2" data-format="branch" data-dropdown-css-class="branches" class="pull-right">
-                @defining(RepositoryService.getRepository(project).getBranchNames()) { branches =>
-                    @for(branchName <- branches){
-                        <option value="@routes.CodeHistoryApp.history(project.owner, project.name, URLEncoder.encode(branchName, "UTF-8"), null)"
-                                @if(selectedBranch){ @if(branchItemName(branchName) == branchItemName(selectedBranch)){ selected } }>
-                                @branchName
-                        </option>
-                    }
-                }
-            </select>
-
             <ul class="nav nav-tabs" style="margin-bottom:20px;">
                 <li>
                     <a href="@routes.CodeApp.codeBrowser(project.owner, project.name)">@Messages("code.files")</a>