Filter out soname provides for mozilla gmp plugin
    
    Both mozilla-openh264 and openh264 otherwise provide
    libopenh264.so.7()(64bit) - this is certainly an issue with the build
    scripts that incorrectly set the soname for the gmp plugin, but
    regardless of that there is no point in having virtual provides for a
    plugin soname that is not in the linker search path.