Follow up script renaming

Author: xolox

scripts/pypy.sh

@@ -5,7 +5,7 @@
 
 # Downgrade to pip < 20.2 when running on PyPy inside tox.
 echo "[scripts/pypy.sh] pip before downgrade: $(pip --version)" >&2
-python scripts/downgrade-pip-on-pypy.py
+python scripts/pypy.py
 echo "[scripts/pypy.sh] pip after downgrade: $(pip --version)" >&2
 
 # Continue installing packages as normal.