fix(deps): update dependency express to v4.21.0 [security] (#378)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [express](http://expressjs.com/)
([source](https://redirect.github.com/expressjs/express)) | [`4.20.0` ->
`4.21.0`](https://renovatebot.com/diffs/npm/express/4.20.0/4.21.0) |
[![age](https://developer.mend.io/api/mc/badges/age/npm/express/4.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/express/4.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/express/4.20.0/4.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/express/4.20.0/4.21.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

### GitHub Vulnerability Alerts

####
[CVE-2024-43796](https://redirect.github.com/expressjs/express/security/advisories/GHSA-qw6h-vgh9-j6wx)

### Impact

In express <4.20.0, passing untrusted user input - even after sanitizing
it - to `response.redirect()` may execute untrusted code

### Patches

this issue is patched in express 4.20.0

### Workarounds

users are encouraged to upgrade to the patched version of express, but
otherwise can workaround this issue by making sure any untrusted inputs
are safe, ideally by validating them against an explicit allowlist

### Details

successful exploitation of this vector requires the following:

1. The attacker MUST control the input to response.redirect()
1. express MUST NOT redirect before the template appears
1. the browser MUST NOT complete redirection before:
1. the user MUST click on the link in the template

---

### Release Notes

<details>
<summary>expressjs/express (express)</summary>

###
[`v4.21.0`](https://redirect.github.com/expressjs/express/releases/tag/4.21.0)

[Compare
Source](https://redirect.github.com/expressjs/express/compare/4.20.0...4.21.0)

#### What's Changed

- Deprecate `"back"` magic string in redirects by
[@&#8203;blakeembrey](https://redirect.github.com/blakeembrey) in
[https://github.com/expressjs/express/pull/5935](https://redirect.github.com/expressjs/express/pull/5935)
- [email protected] by
[@&#8203;wesleytodd](https://redirect.github.com/wesleytodd) in
[https://github.com/expressjs/express/pull/5954](https://redirect.github.com/expressjs/express/pull/5954)
- fix(deps): [email protected] by
[@&#8203;wesleytodd](https://redirect.github.com/wesleytodd) in
[https://github.com/expressjs/express/pull/5951](https://redirect.github.com/expressjs/express/pull/5951)
- Upgraded dependency qs to 6.13.0 to match qs in body-parser by
[@&#8203;agadzinski93](https://redirect.github.com/agadzinski93) in
[https://github.com/expressjs/express/pull/5946](https://redirect.github.com/expressjs/express/pull/5946)

#### New Contributors

- [@&#8203;agadzinski93](https://redirect.github.com/agadzinski93) made
their first contribution in
[https://github.com/expressjs/express/pull/5946](https://redirect.github.com/expressjs/express/pull/5946)

**Full Changelog**:
expressjs/express@4.20.0...4.21.0

</details>

---

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package.json

@@ -54,7 +54,7 @@
     "clsx": "^1.2.1",
     "eventemitter3": "^5.0.1",
     "events": "^3.3.0",
-    "express": "4.20.0",
+    "express": "4.21.0",
     "express-validator": "^7.0.1",
     "flagsmith": "^3.21.0",
     "flagsmith-nodejs": "^3.2.0",