github: pin fedora:35 for the pylint check

Fedora 36 ships pylint 2.13 that newly reports:

dnf-json:436:20: E0601: Using variable 'cache_state' before assignment (used-before-assignment)

As dnf-json is pending a big rewrite
(https://github.com/osbuild/osbuild-composer/pull/2537),
I decided to pin fedora to 35 and let the other PR decide how to proceed in
order to prevent any conflicts.

Signed-off-by: Ondřej Budai <ondrej@budai.cz>

.github/workflows/tests.yml

@@ -41,7 +41,7 @@ jobs:
     name: "🐍 Lint (dnf-json)"
     runs-on: ubuntu-latest
     container:
-      image: docker.io/library/fedora:latest
+      image: docker.io/library/fedora:35
     steps:
     - uses: actions/checkout@v2.4.0
     - name: Install dependencies