Remove redundant branch labels from MR form

Fixes #1525

app/views/merge_requests/_form.html.haml

@@ -13,10 +13,7 @@
       .mr_branch_box
         %h5 From (Head Branch)
         .body
-          .padded
-            = f.label :source_branch, "From", class: "control-label"
-            .controls
-              = f.select(:source_branch, @project.heads.map(&:name), { include_blank: "Select branch" }, {class: 'chosen span3'})
+          .padded= f.select(:source_branch, @project.heads.map(&:name), { include_blank: "Select branch" }, {class: 'chosen span4'})
       .mr_source_commit
 
     .span2
@@ -25,10 +22,7 @@
       .mr_branch_box
         %h5 To (Base Branch)
         .body
-          .padded
-            = f.label :target_branch, "To", class: "control-label"
-            .controls
-              = f.select(:target_branch, @project.heads.map(&:name), { include_blank: "Select branch" }, {class: 'chosen span3'})
+          .padded= f.select(:target_branch, @project.heads.map(&:name), { include_blank: "Select branch" }, {class: 'chosen span4'})
       .mr_target_commit
 
   %h4.cdark 2. Fill info