Doc: Move Qt QML from the GPL-only section to the LGPL section

Commits 6a629484 and 8203e055

 on different branches created an undetected
conflict, which made it look like Qt QML is not available under the LGPL

Task-number: QTBUG-54516
Change-Id: I41abe25043181ff1e7599f0fa162dbb16660f397
Reviewed-by: Topi Reiniö <topi.reinio@theqtcompany.com>