[Snyk] Security upgrade express from 4.15.4 to 4.21.0

[j1348]

Snyk has created this PR to fix 3 vulnerabilities in the npm dependencies of this project.

Snyk changed the following file(s):

• package.json

⚠️ Warning

Failed to update the package-lock.json, please update manually before merging.

Vulnerabilities that will be fixed with an upgrade:

	Issue	Score
	Cross-site Scripting SNYK-JS-EXPRESS-7926867	541
	Cross-site Scripting SNYK-JS-SEND-7926862	391
	Cross-site Scripting SNYK-JS-SERVESTATIC-7926865	391

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