chore!: Dropped support for Node 12

[edx-requirements-bot]

BREAKING CHANGE: Dropped support for Node 12

Additional information from script execution

Python code cleanup by the cleanup-python-code Jenkins job.

This pull request was generated by the cleanup-python-code Jenkins job, which ran

modernize_node_workflow
modernize_node_release_workflow
FILE=.nvmrc
if [[ -f "$FILE" ]]; then
    sed -i -E 's/v[0-9]+/v16/g' .nvmrc
fi

The following packages were installed:
edx-repo-tools==0.7.1

[codecov]

Codecov Report

Merging #207 (6d000ea) into master (b66ae65) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #207   +/-   ##
=======================================
  Coverage   70.27%   70.27%           
=======================================
  Files           4        4           
  Lines          37       37           
  Branches        5        5           
=======================================
  Hits           26       26           
  Misses         11       11           

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