Example: Don't accumulate tiny translations in games_fps.html

[ycw]

fix: #28660

Description

The cause is that the example blindly pushes playerCollider away from the intersection normal by depth amount in every frame, so say when player is idling on ramp, the tiny offset will eventually add up >octree_threshold, then octree considers that the playerCollider is not intersecting with the ramp.

This PR fixed that by translating the playerCollider only if intersection's depth >= octree_threshold