Make the F31/RPM testing environment use cchardet

Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>

dev/containers/f31-rpms-py3

@@ -15,6 +15,7 @@ RUN dnf -y --enablerepo=updates-testing install \
     python3-black \
     python3-flake8 \
     python3-pytest-xdist \
+    python3-cchardet \
     redis \
     which \
     git