Opengl Renderer Compresses Images with Different Dimensions

## Description of bug / unexpected behavior

When changing the dimensions of an image to a square in opengl a circle compressed into an oval. When the same code was ran in cairo the shape was preserved as expected.

## Expected behavior

I expected the opengl output to match the cairo output when changing the image's dimensions where the shape is preserved.

## How to reproduce the issue

Code for reproducing the problem
This produced the image unexpectedly.
%%manim --renderer=opengl -r 1080,1080 --write_to_movie -s -v WARNING -ql yes

```py
class yes(Scene):
def construct(self):
config.frame_height = 15
config.frame_width = 15
print(config.frame_height)
print(config.frame_width)
print(config.pixel_height)
print(config.pixel_width)
self.add(Circle(fill_opacity=1,color=BLUE))
```
This produced the image as expected.
%%manim --renderer=cairo -r 1080,1080 --write_to_movie -s -v WARNING -ql yes

```py
class yes(Scene):
def construct(self):
config.frame_height = 15
config.frame_width = 15
print(config.frame_height)
print(config.frame_width)
print(config.pixel_height)
print(config.pixel_width)
self.add(Circle(fill_opacity=1,color=BLUE))
```

## Additional media files

Images/GIFs

Opengl bug
Cairo expected

## Logs
Terminal output

Opengl:

```
[10/02/21 01:37:49] INFO scene_file_writer.py:606
File ready at '/home/theredninja2/jup_f
iles/manim_programs/media/images/manim_
programs/yes_ManimCE_v0.10.0.png'

INFO Rendered yes scene.py:233
Played 0 animations
```

Cairo:

```
[10/02/21 01:35:19] INFO scene_file_writer.py:606
File ready at '/home/theredninja2/jup_f
iles/manim_programs/media/images/manim_
programs/yes_ManimCE_v0.10.0.png'

INFO Rendered yes scene.py:233
Played 0 animations
```

## System specifications

System Details

- OS (with version, e.g Windows 10 v2004 or macOS 10.15 (Catalina)):
- Google Chrome OS Version 93.0.4577.95 (Official Build) (64-bit)
- RAM:
- Unknown
- Python version (`python/py/python3 --version`):
- Python 3.8.11
- Installed modules (provide output from `pip list`):
```
Package Version
------------------- ---------
backcall 0.2.0
certifi 2021.5.30
charset-normalizer 2.0.6
click 8.0.1
click-default-group 1.2.2
cloup 0.7.1
colorama 0.4.4
colour 0.1.5
commonmark 0.9.1
decorator 5.1.0
glcontext 2.3.4
idna 3.2
ipykernel 5.5.3
ipython 7.22.0
ipython-genutils 0.2.0
jedi 0.18.0
jupyter-client 6.1.12
jupyter-core 4.7.1
manim 0.10.0
ManimPango 0.3.0
mapbox-earcut 0.12.10
moderngl 5.6.4
moderngl-window 2.4.0
multipledispatch 0.6.0
networkx 2.6.3
numpy 1.21.2
parso 0.8.2
pexpect 4.8.0
pickleshare 0.7.5
Pillow 8.3.2
pip 21.0.1
prompt-toolkit 3.0.18
ptyprocess 0.7.0
pycairo 1.20.1
pydub 0.25.1
pyglet 1.5.21
Pygments 2.8.1
pyrr 0.10.3
python-dateutil 2.8.1
pyzmq 22.0.3
requests 2.26.0
rich 10.11.0
scipy 1.7.1
screeninfo 0.6.7
setuptools 58.0.4
six 1.15.0
tornado 6.1
tqdm 4.62.3
traitlets 5.0.5
urllib3 1.26.7
watchdog 2.1.5
wcwidth 0.2.5
wheel 0.37.0
```

LaTeX details

+ LaTeX distribution (e.g. TeX Live 2020):
+ Installed LaTeX packages:

No output.
FFMPEG

Output of `ffmpeg -version`:

```
ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
```

## Additional comments

Reproduce the supplied Scene with the OpenGL and Cairo renderers using a square 1080x1080 output and compare the circle dimensions. Start from the OpenGL renderer path selected by `--renderer=opengl`; done means the OpenGL output preserves the circle's shape when frame and pixel dimensions are changed as in the report.

Written by the indexing model from the issue text.