Why does the latter half of my code box display a gray vertical line after a certain length?

[windgodovo]

Describe the current behavior
As shown in the image, there's a vertical line running through the text in the latter half of my code block. How can I remove it?

What web browser you are using
Chrome, Firefox

Additional context
Link to a minimal, public, self-contained notebook that reproduces this issue.

https://colab.research.google.com/drive/1eE7snijIH7Jd87u5OheLUbz8UFO249iA?usp=sharing

[beholder4096]

I though that was an actual feature, yeah, I guess not.