ci: restore distutils via setuptools<81 instead of pinning Python

Reverts the workflow pin. Keeping setup-python at "3.x" avoids the
workflow-modification approval gate on fork PRs; adding setuptools<81 to
the dev requirements restores the vendored distutils that fixit==0.1.4
imports (distutils was removed from CPython 3.12).

Author: priya-sundaram-dev

.github/workflows/main.yml

@@ -12,9 +12,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
         with:
-          # fixit 0.1.4 imports the stdlib ``distutils`` module, which was removed
-          # in Python 3.12. Pin to 3.11 until the fixit pin is upgraded.
-          python-version: "3.11"
+          python-version: "3.x"
       - uses: actions/cache@v3
         with:
           path: |

requirements-dev.txt

@@ -3,3 +3,6 @@ pytest==7.4.2
 pytest-aiohttp==1.0.5
 pytest-asyncio==0.21.1
 pytest-cov==4.1.0
+# setuptools<81 still vendors the stdlib ``distutils`` (removed from CPython in
+# 3.12); fixit==0.1.4 imports it, so keep the shim available under "3.x" CI.
+setuptools<81