[misc] Updated page to the new XAR format

(cherry picked from commit bae309a86df025c3caf94a53f3e35764df38a3c4)
XWIKI-10932: Try to have the same height for "Variables" and "Preview" boxes on Flamingo Theme

* Increasing the height mannualy

(cherry picked from commit 70981d63aa786cb5189716d5f7ba5ace51dee645)
XWIKI-10932: Try to have the same height for "Variables" and "Preview" boxes on Flamingo Theme

* Added a ‘row’ container in order to hold the grid elements, thus
better aligning components
* Removed ‘div’ from the id selectors

(cherry picked from commit 0a602b22d21e1a43d49322278fb9a5cb17c03477)