Terminal defocuses upon scene selection prompt when using the OpenGL renderer

## Description of bug / unexpected behavior
Running a file with multiple scenes without specifying the Scene to render in the command, such as this:

```py
from manim import *

class SphereTest(Scene):
def construct(self):
a = Sphere()
self.play(Create(a))
self.interactive_embed()

class P(Scene):
def func(self, u, v):
return np.array([np.cos(u) * np.cos(v), np.cos(u) * np.sin(v), u])

def construct(self):
axes = ThreeDAxes(x_range=[-4,4], x_length=8)
surface = ParametricSurface(
lambda u, v: axes.c2p(*self.func(u, v)),
u_min=-PI,
u_max=PI,
v_min=0,
v_max=TAU,
)
# self.set_camera_orientation(theta=70 * DEGREES, phi=75 * DEGREES)
self.add(axes, surface)
self.interactive_embed()
```

correctly brings up the scene selector:

```
C:\Users\Daryl\manim-videos\manim-videos>manim -p --renderer=opengl opengltests.py
Manim Community v0.8.0

1: P
2: SphereTest

Choose number corresponding to desired scene/arguments.
(Use comma separated list for multiple entries)
Choice(s):
```

but the terminal defocuses, requiring the user to click on it again to type in the number. This can be slightly annoying.

## Expected behavior

## How to reproduce the issue

Code for reproducing the problem

```py
Paste your code here.
```

## Additional media files

Images/GIFs

## Logs
Terminal output

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

## System specifications

System Details

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

LaTeX details

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

FFMPEG

Output of `ffmpeg -version`:

```
PASTE HERE
```

## Additional comments

Reproduce the issue with the command shown in the report, using the OpenGL renderer and a file containing multiple scenes. Start at the scene-selection prompt and verify that entering a choice works without clicking the terminal; done means the terminal retains focus when the prompt appears.

Written by the indexing model from the issue text.