Fix our use of --use-wheel in pip. (#4269)

* Fix our use of `--use-wheel` in pip.

Refs #4262

* Update common branch

Author: ericholscher

readthedocs/doc_builder/python_environments.py

@@ -253,7 +253,6 @@ def install_core_requirements(self):
             'python',
             self.venv_bin(filename='pip'),
             'install',
-            '--use-wheel',
             '--upgrade',
             '--cache-dir',
             self.project.pip_cache_path,

readthedocs/rtd_tests/tests/test_doc_building.py

@@ -1137,7 +1137,6 @@ def setUp(self):
             'python',
             mock.ANY,  # pip path
             'install',
-            '--use-wheel',
             '--upgrade',
             '--cache-dir',
             mock.ANY,  # cache path