flatpak version uses very old SDKs

[rezad1393]

Info: runtime org.kde.Platform branch 5.15 is end-of-life, with reason:
   We strongly recommend moving to the latest stable version of the Plaform and SDK
Info: applications using this runtime:
   net.mediaarea.QCTools

Info: runtime org.freedesktop.Platform.GL.default branch 20.08 is end-of-life, with reason:
   org.freedesktop.Platform 20.08 is no longer receiving fixes and security updates. Please update to a supported runtime version.
Info: applications using this runtime:
   net.mediaarea.QCTools

[g-maxime]

Fixed by flathub/net.mediaarea.QCTools#7