Use GitHub project for contributor lists instead of a file

[lornajane]

Fixes #4148 by removing the file.

[ralfhandl]

@handrews Will dev, v3.1-dev, and v3.2-dev be updated from main after merging this?

[handrews]

@ralfhandl up to the TSC. I definitely do not want to be the person in charge of approving every branch/merge step.

[lornajane]

Yes, we'll merge main into those dev branches on an informal schedule - I suggest we work through more of these docs updates and then do some dev branch updates to keep everyone aligned.