package/qt6/qt6serialport: fix license

Commit 343974b9 forgot to change the
licensing information which has been updated with
https://code.qt.io/cgit/qt/qtserialport.git/commit/?id=bb05a26d52c834cc7f3c549f3e5d66f76baf42a2


resulting in the following build failure:

ERROR: LICENSE.GPL2 has wrong sha256 hash:
ERROR: expected: 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643
ERROR: got     :

Fixes:
 - No autobuilder failures yet

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr: one-item per line]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>