LinearTransformationScene: wrong scaling in self.plane.p2c()

## Description of bug / unexpected behavior
Manim 0.17.2

The method self.plane.point_to_coords() returns wrong values.

## Expected behavior
The following script places a Dot() on the position (1,1) of both the background numberplane and the transformed numberplane. Reading back the respective coordinates from the dots' Dot().get_center() results in wrong values for the transformed numberplane.

The background numberplane correctly returns (1,1)

The transformed numberplane returns (1.5547002, 1.5547002)

## How to reproduce the issue
Code for reproducing the problem

```py
class c(LinearTransformationScene):

def __init__(self):
LinearTransformationScene.__init__(self, show_coordinates=True,
i_hat_color= GREEN,
j_hat_color=RED,
include_background_plane= True)

def construct(self):
matrix = [[1,2/np.sqrt(13)], [0, 3/np.sqrt(13)]]

self.apply_matrix(matrix)

dot1=Dot().set_color(GREEN).move_to(self.background_plane.c2p(1,1))
dot2=Dot().set_color(RED).move_to(self.plane.c2p(1,1))
self.add(dot1)
self.add(dot2)
print(self.background_plane.p2c(dot1.get_center()))
print(self.plane.p2c(dot2.get_center()))
self.wait()
```

## Additional media files

Images/GIFs

## Logs
Terminal output

```
PASTE HERE OR PROVIDE LINK TO https://pastebin.com/ OR SIMILAR
```

## System specifications

System Details

- OS Windows 10 64 bit
- Python version 3.9.8

Run the provided reproduction with LinearTransformationScene and compare background_plane.p2c() with plane.p2c() after apply_matrix(). Trace the plane coordinate conversion used by self.plane.p2c() and point_to_coords(); done means the transformed plane returns (1, 1) for the dot placed at transformed coordinates without breaking the background plane behavior.

Written by the indexing model from the issue text.