Bump immutable from 4.3.4 to 4.3.8 in /demo/frontend

Bumps [immutable](https://github.com/immutable-js/immutable-js) from 4.3.4 to 4.3.8.
- [Release notes](https://github.com/immutable-js/immutable-js/releases)
- [Changelog](https://github.com/immutable-js/immutable-js/blob/main/CHANGELOG.md)
- [Commits](https://github.com/immutable-js/immutable-js/compare/v4.3.4...v4.3.8)

---
updated-dependencies:
- dependency-name: immutable
  dependency-version: 4.3.8
  dependency-type: indirect
...

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

demo/frontend/yarn.lock

@@ -2479,9 +2479,9 @@ immutability-helper@^3.1.1:
   integrity sha512-Q0QaXjPjwIju/28TsugCHNEASwoCcJSyJV3uO1sOIQGI0jKgm9f41Lvz0DZj3n46cNCyAZTsEYoY4C2bVRUzyQ==
 
 immutable@^4.0.0:
-  version "4.3.4"
-  resolved "https://registry.yarnpkg.com/immutable/-/immutable-4.3.4.tgz#2e07b33837b4bb7662f288c244d1ced1ef65a78f"
-  integrity sha512-fsXeu4J4i6WNWSikpI88v/PcVflZz+6kMhUfIwc5SY+poQRPnaf5V7qds6SUyUN3cVxEzuCab7QIoLOQ+DQ1wA==
+  version "4.3.8"
+  resolved "https://registry.yarnpkg.com/immutable/-/immutable-4.3.8.tgz#02d183c7727fb2bb1d5d0380da0d779dce9296a7"
+  integrity sha512-d/Ld9aLbKpNwyl0KiM2CT1WYvkitQ1TSvmRtkcV8FKStiDoA7Slzgjmb/1G2yhKM1p0XeNOieaTbFZmU1d3Xuw==
 
 import-fresh@^2.0.0:
   version "2.0.0"