Fix MovingCamera and ZoomedScene

[leotrs]

#330 broke MovingCamera and ZoomedScene. This is a quick attempt at a hotfix.

Draft since we're still working on it.

[Aathish04]

@leotrs If it's fine, I'll add the test scene I used as a test for this once #335 is merged.

[leotrs]

@Aathish04 I believe we can come back to this and finish now.

[Aathish04]

Alright, so I had originally intended to do pixel comparison tests, just like the ones that were done for Text, TexMobject and TextMobject. However, with #335 basically confirming that they are too erratic and way too precise to be of any use, I don't think that such a test will be useful in this case as well.

@leotrs @huguesdevimeux Do you have any other suggestions as to how a test for this could be written? I can't think of any straightforward ones, since even if the classes are broken, they could still render and the only difference would be in the final video.

[leotrs]

This was intended to be a hotfix - can we merge it while we think of ways to test these?

[Aathish04]

This was intended to be a hotfix - can we merge it while we think of ways to test these?

Yes, that would be good.

Adding this test to #193