ci: update GH actions and conda.yml

[davidyuk]

Fixes warning

Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: actions/checkout@v2, actions/setup-python@v2, actions/cache@v2

This PR is supported by the Æternity Crypto Foundation

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (26014b7) 82.50% compared to head (5b1e4c7) 82.50%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1807   +/-   ##
========================================
  Coverage    82.50%   82.50%           
========================================
  Files           90       90           
  Lines         3104     3104           
  Branches       618      618           
========================================
  Hits          2561     2561           
  Misses         251      251           
  Partials       292      292           

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