`Surface` has incorrect checkerboard coloring

## Description of bug / unexpected behavior
I tried rendering a sphere with `manim.Surface`, and the checkerboard coloring is not alternating properly.
This is evident in the 2nd and 3rd row above the horizontal plane in the screenshot section below.

## Expected behavior
The code should create a spherical surface which each cell having alternating, checkerboard colors.

## How to reproduce the issue

Code for reproducing the problem

```py
from manim import *

class ParaSphereDemo(ThreeDScene):
def construct(self):
axes = ThreeDAxes()
sphere = Surface(
lambda u, v: axes.c2p(
*np.array([
np.sin(u) * np.cos(v),
np.sin(u) * np.sin(v),
np.cos(u)
])
),
u_range=(-np.pi, np.pi),
v_range=(-np.pi, np.pi),
checkerboard_colors=False
)
self.set_camera_orientation(phi=75 * DEGREES, theta=30 * DEGREES)
self.add(axes, sphere)
```

## Additional media files

Images/GIFs

## Additional comments
I've already fixed this and will submit a PR soon.

Start with the provided Python reproducer and inspect the Surface entry point, focusing on how its checkerboard colors are assigned across the u and v ranges. Compare the rendered rows with the expected alternating pattern, then verify that the sphere example produces alternating colors in every cell. The issue notes that a fix has already been made and a pull request is forthcoming.

Written by the indexing model from the issue text.