build: pypy 3.9 doesn't seem to be available nightly

Author: nedbat

.github/workflows/python-nightly.yml

@@ -60,7 +60,6 @@ jobs:
           - "3.13-dev"
           - "3.14-dev"
           # https://github.com/actions/setup-python#available-versions-of-pypy
-          - "pypy-3.9-nightly"
           - "pypy-3.10-nightly"
         nogil:
           - false