CI: update opensuse platforms

PR #173

Author: mkoeppe

.github/workflows/ci-sage.yml

@@ -97,7 +97,8 @@ jobs:
            "centos-stream-8",
            "gentoo-python3.9",
            "archlinux-latest",
-           "opensuse-15.4",
+           "opensuse-15.4-gcc_11",
+           "opensuse-tumbleweed",
            "conda-forge",
            ]
       tox_packages_factors: >-