Bug 29680: Change markup to correct button radius

Bug 29680: Change markup to correct button radius

This patch alters the markup around the "Show SQL/Hide SQL" buttons so
that they are not styled as if they are a button group.

To test, apply the patch and run an SQL report.

The "Show SQL code" button should be styled consistently with other
single buttons in the toolbar. Click it to test that the "Hide SQL code"
button is also correct.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Andreas Roussos <a.roussos@dataly.gr>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>