Update dependency express to ^4.21.0

This MR contains the following updates:

Package	Type	Update	Change
express (source)	dependencies	minor	^4.20.0 -> ^4.21.0

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Release Notes

expressjs/express (express)

v4.21.0

Compare Source

What's Changed

• Deprecate "back" magic string in redirects by @​blakeembrey in https://github.com/expressjs/express/pull/5935
• finalhandler@1.3.1 by @​wesleytodd in https://github.com/expressjs/express/pull/5954
• fix(deps): serve-static@1.16.2 by @​wesleytodd in https://github.com/expressjs/express/pull/5951
• Upgraded dependency qs to 6.13.0 to match qs in body-parser by @​agadzinski93 in https://github.com/expressjs/express/pull/5946

New Contributors

• @​agadzinski93 made their first contribution in https://github.com/expressjs/express/pull/5946

Full Changelog: https://github.com/expressjs/express/compare/4.20.0...4.21.0

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