Update libqt5-qtwebkit to rev 55 via SR 789353
    
    https://build.opensuse.org/request/show/789353
    by user cgiboudeaux + maxlin_factory
    - Use Ninja with CMake to improve build times by circa 300%
    - Fix a few typos in libqt5-qtwebkit.spec
    
    - New upstream release
    - Drop patches
      * icu-build-fix.patch
      * qt5.15-workaround.patch
    
    - Add patch to fix build against Qt 5.15:
      * qt5.15-workaround.patch