Update version of gunicorn

[gmmajal]

Relevant issue: #26

Background info:

• safety has flagged the followed CVE(https://data.safetycli.com/v/72809/f17/). gunicorn should be bumped to v23.0.0

Changes introduced:

• gunicorn v23.0.0 is used inside the Dockerfile.
• For the patch release the author names, release date and version number has been updated.
• The version number has been updated inside the pyproject.toml file.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.54%. Comparing base (df1cf7d) to head (656fc83).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #28   +/-   ##
=======================================
  Coverage   94.54%   94.54%           
=======================================
  Files          23       23           
  Lines         898      898           
=======================================
  Hits          849      849           
  Misses         49       49           

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[gmmajal]

The pull request template file has been moved to the .github folder. The sub-folder named PULL_REQUEST_TEMPLATE has been deleted. This sub-folder is only needed when multiple templates are present. As we only have one right now, we don't need this sub-folder.

[gmmajal]

Successfully built the image of qualle locally using the updated Dockerfile. Tested the rest api and it seems to be working smoothly with the new version of gunicorn