coolreader: license change from GPLv2 to GPLv2+ and GUI from Qt4 to Qt5

[Andy Mender]

Hello,

The license of coolreader was previously set to GPLv2 in the SPEC file,
however per the short discussion in a related thread, it was always GPLv2+:
https://github.com/buggins/coolreader/issues/80

This was now amended and a PR with the license file itself submitted to
upstream: https://github.com/buggins/coolreader/pull/205

In addition, upstream at some point changed the main tested GUI from QT
(Qt4) to QT5 (Qt5). I tried triaging the many source code related build
failures for Qt4, but it's pretty clear Qt4 is no longer their main focus.
Thus, I switched to Qt5 in the SPEC file.

The change already landed in Fedora 34/Rawhide.

Repo: https://src.fedoraproject.org/rpms/coolreader

Cheers,
Andy