Don't reimplement ThumbCreator::flags()

It does the same thing as the default implementation

ffmpegthumbnailer.cpp

@@ -171,11 +171,6 @@ bool FFMpegThumbnailer::create(const QString& path, int width, int /*height*/, Q
     return false;
 }
 
-ThumbCreator::Flags FFMpegThumbnailer::flags() const
-{
-    return (Flags)(None);
-}
-
 void FFMpegThumbnailer::updateSequenceIndexWraparoundPoint(float offset)
 {
     float wraparoundPoint = offset;

ffmpegthumbnailer.h

@@ -30,7 +30,6 @@ public:
     FFMpegThumbnailer();
     ~FFMpegThumbnailer() override;
     bool create(const QString& path, int width, int height, QImage& img) override;
-    Flags flags() const override;
 
 private:
     void updateSequenceIndexWraparoundPoint(float offset);