player: Return type nullability is wrong on quite a few (enum/flag) methods
When !630 (merged) + https://github.com/gtk-rs/gir/pull/991 land gstreamer-player gets quite a few new functions that incorrectly return Option<...>.
We have decided to not waste time finding and overriding those in Gir.toml but instead "wait" for someone to do another nullability pass on the C code and annotations. After all @slomo initially thought it was ready, so it can't be too far off