[Snyk] Security upgrade express from 4.20.0 to 4.21.1

[satkunas]

Snyk has created this PR to fix 1 vulnerabilities in the npm dependencies of this project.

Snyk changed the following file(s):

• t/mock_servers/node_radius/package.json
• t/mock_servers/node_radius/package-lock.json

Vulnerabilities that will be fixed with an upgrade:

	Issue	Score
	Cross-site Scripting (XSS) SNYK-JS-COOKIE-8163060	601

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🦉 Cross-site Scripting (XSS)

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