style(MatrixTestResult): Increase column width

`4em` is too narrow for texts like `6 hr 17 min` to fit into: It is shown on two lines as:
> 6 hr 17
> min

The German translation is even worse, which spans 4 lines:
> 6
> Stunden
> 17
> Minuten

which make the table to take up too much space.

src/main/resources/hudson/tasks/test/MatrixTestResult/index.jelly

@@ -33,7 +33,7 @@ THE SOFTWARE.
       <table class="pane sortable bigtable">
         <tr>
           <td class="pane-header">Configuration Name</td>
-          <td class="pane-header" style="width:4em;text-align:right">Duration</td>
+          <td class="pane-header" style="width:6em;text-align:right">Duration</td>
           <td class="pane-header" style="width:4em;text-align:right">All</td>
           <td class="pane-header" style="width:4em;text-align:right">Failed</td>
           <td class="pane-header" style="width:4em;text-align:right">Skipped</td>