[Snyk] Security upgrade mjml from 4.4.0-beta.2 to 4.4.0

[snyk-bot]

Snyk has created this PR to fix one or more vulnerable packages in the `npm` dependencies of this project.

Changes included in this PR

• Changes to the following files to upgrade the vulnerable dependencies to a fixed version:
  • server/package.json
  • server/package-lock.json

Vulnerabilities that will be fixed

With an upgrade:

Severity	Issue	Breaking Change	Exploit Maturity
	Prototype Pollution SNYK-JS-MINIMIST-559764	No	Proof of Concept

Check the changes in this PR to ensure they won't cause issues with your project.

---

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For more information:

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📚 Read more about Snyk's upgrade and patch logic

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 49.75%. Comparing base (22279ba) to head (1a52485).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #660   +/-   ##
=======================================
  Coverage   49.75%   49.75%           
=======================================
  Files         126      126           
  Lines        1411     1411           
  Branches      341      341           
=======================================
  Hits          702      702           
  Misses        671      671           
  Partials       38       38           

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