Use Podman instead of Docker for Selenium test

[ricardobranco777]

This PR:

• Uses Podman instead of Docker for the Selenium test.
• Fixes the cleanup code to remove the image afterwards.

Because this test builds a Docker image it may take some time if the layers aren't cached. Set the SKIP_SELENIUM environment variable when running pytest or make test.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (0a413fb) 78.56% compared to head (b4a50d8) 78.56%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #288   +/-   ##
=======================================
  Coverage   78.56%   78.56%           
=======================================
  Files          21       21           
  Lines        1549     1549           
=======================================
  Hits         1217     1217           
  Misses        332      332           

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