surf_beginner & surf_beginner_hell stair sliding breaking s4 sc

[tomtko]

Stair sliding fix is being applied to the client when doing the s4 shortcut on both versions of these maps

[2169] EndTouch 218
[2210] Collision predicted! (normal: -0.216 -0.773 0.595)
[2305] Collision predicted! (normal: -0.163 -0.773 0.611)
[2359] Collision predicted! (normal: 1.000 0.000 0.000)
[2360] Landed
[2360] DO FIX: Stair Sliding
[2362] Collision predicted! (normal: 0.000 0.000 0.000)
[2364] DO FIX: Stair Sliding

If that's useful