Remove dependency on unused sql module

Change-Id: I102bcb81ec53d022480e81a3632b93d42bf33403
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>
Reviewed-by: Davide Pesavento <davidepesa@gmail.com>

src/websockets/websockets.pro

 load(qt_build_config)
 TARGET = QtWebSockets
 
-QT = core network core-private sql
+QT = core network core-private
 
 TEMPLATE = lib