Add bandit job to Github workflows

[lcmtwn]

closes #1550

• add bandit job to Github workflows
• remove bandit job from Travis CI
• remove bandit package from requirements

[codecov]

Codecov Report

Merging #1576 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1576   +/-   ##
=======================================
  Coverage   76.26%   76.26%           
=======================================
  Files         123      123           
  Lines        4580     4580           
  Branches      547      547           
=======================================
  Hits         3493     3493           
  Misses        912      912           
  Partials      175      175           

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[atodorov]

LGTM, just add Closes #1550 in your commit log and this would be good to go.