Remove manylinux CI workflow

[jonathangreen]

@jimjag how do you feel about deleting the manylinux.yml workflow as well? The wheel build workflow does basically the same thing, and deleting it would get CI passing on this repo again.

[jimjag]

I'm hesitant to remove it since it provides insight into how things will work on AWS and various PaaS environments, such as Heroku. Let's see if we can clean it up 1st.

[jonathangreen]

@jimjag can you clarify what this workflow is doing that should be tested that wheels.yml isn't already doing?

Both the workflows build a wheel using the manylinux containers. The wheels.yml workflow is more automated, and builds for more targets. So I don't see much value in this workflow.

[jonathangreen]

I'll close this one then, since @jimjag isn't interested in it.