Revert 2em notebook header space

IPython/html/static/notebook/less/notebook.less

@@ -1,77 +1,77 b''
 
 body {
     background-color:   @body-bg;
 }
 
 body.notebook_app {
     overflow: hidden;
 }
 
 @media (max-width: 767px) {
     // remove bootstrap-responsive's body padding on small screens
     body.notebook_app {
         padding-left: 0px;
         padding-right: 0px;
     }
 }
 
 span#notebook_name {
     height: 1em;
     line-height: 1em;
     padding: 3px;
     border: none;
     font-size: 146.5%;
 }
 
 div#notebook_panel {
     margin: 0px 0px 0px 0px;
     padding: 0px;
     .box-shadow(inset 1px 4px 13px -6px rgba(0,0,0,0.2));
 }
 div#notebook {
     font-size: @notebook_font_size;
     line-height: @notebook_line_height;
     overflow-y: scroll;
     overflow-x: auto;
     width: 100%;
     /* This spaces the cell away from the edge of the notebook area */
-    padding: 2em 0 1em 0;
+    padding: 1em 0 1em 0;
     margin: 0px;
     border-top: 1px solid @navbar-default-border;
     outline: none;
     .border-box-sizing();
 }
 
 div.ui-widget-content {
     border: 1px solid @border_color;
     outline: none;
 }
 
 pre.dialog {
     background-color: @cell_background;
     border: 1px solid #ddd;
     .corner-all;
     padding: 0.4em;
     padding-left: 2em;
 }
 
 p.dialog {
     padding : 0.2em;
 }
 
 /* Word-wrap output correctly.  This is the CSS3 spelling, though Firefox seems
    to not honor it correctly.  Webkit browsers (Chrome, rekonq, Safari) do.
  */
 pre, code, kbd, samp { white-space: pre-wrap; }
 
 #fonttest {
     font-family: @font-family-monospace;
 }
 
 p {
     margin-bottom:0;
 }
 
 .end_space {
     height: 200px;
 }