move to latest selenium image

This could go too far the opposite direction, but I'd rather see
failures because of selenium updates than get a false sense of security
from being on an older version.

Consumers of widgetastic will want to be on the latest version of
selenium

.github/workflows/test_suite.yml

@@ -22,7 +22,7 @@ jobs:
 
     steps:
       - name: Pull selenium-standalone:latest
-        run: podman pull selenium/standalone-${{ matrix.browser }}:4.9
+        run: podman pull selenium/standalone-${{ matrix.browser }}:latest
 
       - name: Pull docker.io/library/nginx:alpine
         run: podman pull docker.io/library/nginx:alpine