package/qt: drop option for license approved

package/qt: drop option for license approved

As stated in previous commits, Buildroot only ever uses the free
license, and we do not have a click-wrap approval for any such free
license for any other package.

The option to approve the license now has no prompt and is no longer
used anywhere.

Legacy handling is not added because it is not useful: when the option
was enabled, it meant "accept the open source license", which is now the
default and only existing behavior.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Julien Corjon <corjon.j@ecagroup.com>
Cc: Peter Seiderer <ps.report@gmx.net>
[Thomas: remove legacy handling as suggested by Arnout.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>