Update Cheetah3 dependency

[thomas-bc]

Related Issue(s)
Has Unit Tests (y/n)
Documentation Included (y/n)

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Change Description

Removes Cheetah3 dependency and adds in the new package name CT3. Same package, different pypi target.

pip install fprime-tools installs Cheetah3 even if CT3 is already installed, because pip doesn't recognize them to be the same packages

$ pip freeze | grep C                                                                                                                                                                                                                            
Cheetah3==3.2.6.post1
CT3==3.3.3.post1