Arrow tip size and stroke width changes with linear transformation scene

## Description of bug / unexpected behavior
In all 3B1B videos the vector arrows have consistent stroke width and tip size during a transformation, so if I set `stroke_width` and `tip_length` for `Arrow` I expected the size of them stay the same during transformation. However, both of them changes along with the transformation.

## Expected behavior
Like any 3B1B video, arrow stroke width and tip length should be static during transformation.

## How to reproduce the issue

```py
class VectorArrow(LinearTransformationScene):
def __init__(self, **kwargs):
LinearTransformationScene.__init__(
self,
show_basis_vectors=False
)

def construct(self):
self.add_vector(Arrow(ORIGIN, [1,2,0], stroke_width=2, tip_length=0.2, buff=0))
self.apply_matrix([[1,1],[0,1]])
```

## Additional media files

Images/GIFs

## Logs
Terminal output

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```

## System specifications

System Details

- OS (with version, e.g Windows 10 v2004 or macOS 10.15 (Catalina)):
- RAM:
- Python version (`python/py/python3 --version`):
- Installed modules (provide output from `pip list`):
```
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```

LaTeX details

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

FFMPEG

Output of `ffmpeg -version`:

```
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```

## Additional comments

Start by reproducing the provided example with Arrow, LinearTransformationScene, and apply_matrix. Trace how the arrow is transformed and compare stroke_width and tip_length before and after the linear transformation. Done means both remain visually constant while the arrow changes position and direction.

Written by the indexing model from the issue text.