Add go/security-advisories redirection (dart-lang#5459)

For now this points at the issue tracking the documentation. The go link
is to be used in the dart sdk changelog.

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Co-authored-by: Anthony Sansone <atsansone@users.noreply.github.com>
Co-authored-by: Parker Lougheed <parlough@gmail.com>

firebase.json

@@ -182,6 +182,7 @@
       { "source": "/go/publishing-with-service-account", "destination": "/tools/pub/automated-publishing#publishing-from-google-cloud-build", "type": 301 },
       { "source": "/go/sdk-constraint", "destination": "/tools/pub/pubspec#sdk-constraints", "type": 301 },
       { "source": "/go/sdk-version-pinning", "destination": "https://github.com/dart-lang/sdk/wiki/Flutter-Pinned-Packages", "type": 301 },
+      { "source": "/go/pub-security-advisories", "destination": "https://github.com/dart-lang/site-www/issues/5458", "type": 301 },
       { "source": "/go/test-docs/:page*", "destination": "https://github.com/dart-lang/test/blob/master/pkgs/test/doc/:page*", "type": 301 },
       { "source": "/go/unsound-null-safety", "destination": "/null-safety/unsound-null-safety", "type": 301 },