Remove equality comparison implementation from `BeatmapCard`
Remove equality comparison implementation from `BeatmapCard`

This turned out to be a hurdle instead as it disallows adding two
beatmap cards of equal beatmap, which, while being a good behaviour in
client, makes tests more complicated to work.

peppy/osu,peppy/osu,ppy/osu,ppy/osu,ppy/osu,peppy/osu