ci: Temporarily disable Archlinux testing

The build of the docker image currently fails due to a bug unrelated to
TW [1]. This will be reverted once the issue is fixed.

[1] https://bugs.archlinux.org/task/69563

.github/workflows/tests.yaml

@@ -36,9 +36,6 @@ jobs:
           - name: "OpenSUSE 15.0"
             runner: ubuntu-latest
             dockerfile: opensuse1500
-          - name: "Archlinux Base (Rolling)"
-            runner: ubuntu-latest
-            dockerfile: arch
           - name: "Mac OS X 10.13"
             runner: macos-latest
             dockerfile: osx