Remove redundant transform method in Geometry singleton

[Xrayez]

Transform2D's xform method can be used instead which handles PoolVector2Array now (as well as 3D version), see #31761.

var trans = Transform2D(0, Vector2(100, 100))

var points = PoolVector2Array([Vector2(0, 0), Vector2(1, 0), Vector2(1, 1), Vector2(0, 1)])

points = Geometry.transform_points_2d(points, trans) # before
points = trans.xform(points) # after

[akien-mga]

Thanks!