chore(deps): Bump dompurify in /build/frontend-legacy

Bumps [dompurify](https://github.com/cure53/DOMPurify) from 3.3.3 to 3.4.0.
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](cure53/DOMPurify@3.3.3...3.4.0)

---
updated-dependencies:
- dependency-name: dompurify
  dependency-version: 3.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

build/frontend-legacy/package-lock.json

@@ -62,7 +62,7 @@
     "crypto-browserify": "^3.12.1",
     "davclient.js": "nextcloud-deps/davclient.js#59d7777d7fe290c5f1fd74a58e7eb529b63e153d",
     "debounce": "^3.0.0",
-    "dompurify": "^3.3.3",
+    "dompurify": "^3.4.0",
     "escape-html": "^1.0.3",
     "focus-trap": "^7.8.0",
     "handlebars": "^4.7.9",