Replace 'cairocffi' by 'pycairo'

[mondeja]

Following from discussion in Zulko/moviepy#1472, this pull replaces cairocffi by pycairo:

• I've tested manually (Ubuntu) all the examples in README and the examples/ directory and works es expected. Some performance tests confirms that pycairo runs faster than cairocffi, because is written directly in C.
• I've tested all the examples in Windows using this workflow and works with an standalone installation. You can download the resulted images from here (below in the section "Artifacts"). As I said in the linked issue, the .dll for Windows is contained in Pycairo wheels since v1.20.0.
• The rest of most common operative systems must install Cairo as usual.
• I've fixed an issue with gcd that has been deprecated from fractions module since Python3.5 and removed in Python3.9, in roses.py example.

So, this change brings:

• Standalone support for Windows.
• Performance increase.
• Example fix.

[DanielFHenriques]

Hello, is there plans to get this merged?