Task #7638: Fix ansible_python_interpreter issues in pulp_installer
pulp_installer role READMEs should not tell users to set ansible_python_interpreter
Multiple roles' README.md files list under variables:
ansible_python_interpreter`: **Required**. Path to the Python interpreter.
It definitely isn't required to be set, since the default behavior is auto_legacy in Ansible 2.8 through 2.11, and auto in 2.12 (planned.)
Furthermore, we probably shouldn't even list it. It is a common built-in Ansible variable that. There are many others, and there seems to be nothing special about it. Perhaps we should list it in case users are running Fedora 30.