Circles intro sequence should use the slider background instead of the triangles one

[N0Y0U2114]

Pretty self explanitory. In stable it uses this dynamic background (called "slider" on merch)

In lazer it uses the same background as the triangles intro sequence

It should use the same one as stable to complete the trifecta of intro sequences.

[N0Y0U2114]

ppy/osu-resources#353 and #31730

[peppy]

I guess we can do this... but it wasn't really the direction I was thinking. The stable backgrounds have historically changed every few years, and they aren't really attached to a certain "skin".

[N0Y0U2114]

Are there plans to continue to change the background given that stable is at the end of its gaining new features life? I would think that the new backgrounds would continue through lazer