chore: install GH master of 'cffi' on Python3.13 harder

.github/workflows/tests.yml

@@ -207,8 +207,6 @@ jobs:
       - name: Install persistent and dependencies (3.13.0-alpha - 3.13.0)
         if: matrix.python-version == '3.13.0-alpha - 3.13.0'
         run: |
-          # Remove this hack once 'cffi' has a release supporting Python 3.13.
-          pip install -e "git+https://github.com/python-cffi/cffi.git#egg=cffi"
           # Install to collect dependencies into the (pip) cache.
           # Use "--pre" here because dependencies with support for this future
           # Python release may only be available as pre-releases
@@ -336,6 +334,8 @@ jobs:
         if: matrix.python-version == '3.13.0-alpha - 3.13.0'
         run: |
           pip install -U wheel setuptools
+          # Remove this hack once 'cffi' has a release supporting Python 3.13.
+          pip install -e "git+https://github.com/python-cffi/cffi.git#egg=cffi"
           # coverage might have a wheel on PyPI for a future python version which is
           # not ABI compatible with the current one, so build it from sdist:
           pip install -U --no-binary :all: coverage