Fix #5268: remove :not(), not supported by Flying Saucer

I am not sure why we needed it: we had a comment saying "Exclude
buttons, as we don't want them to take the whole width of the cell”,
but a button inside a cell doesn’t take that whole width even without
the :not(), and this also the case with the css-grid grid markup, so I
imagine that something else must have changed making this unnecessary.

form-runner/jvm/src/main/assets/xbl/orbeon/grid/grid.less

@@ -85,8 +85,7 @@
             // Instead use a margin on the control inside the cell (see below)
             padding: 0;
 
-            // Exclude buttons, as we don't want them to take the whole width of the cell
-            &> .xforms-control:not(.xforms-trigger-appearance-full),
+            &> .xforms-control,
             &> .xbl-component,
             &> .xforms-group {
                 margin: @frGridCellPadding @frGridCellPadding;