Drop base images

[ricardobranco777]

Drop base images as it creates an issue where dependencies introduced via requirements.txt are not properly tested in CI.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 78.17%. Comparing base (8ec0cb6) to head (c61d2e6).
Report is 1 commits behind head on master.

Files	Patch %	Lines
ocw/lib/emailnotify.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #376   +/-   ##
=======================================
  Coverage   78.17%   78.17%           
=======================================
  Files          22       22           
  Lines        1676     1676           
=======================================
  Hits         1310     1310           
  Misses        366      366           

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[asmorodskyi]

just for the reference PR where base image was introduced https://github.com/SUSE/pcw/pull/350/files