Bump node from 19.8.1 to 21.5.0 in /src/app/AlwaysOn.UI (#1220)

Bumps node from 19.8.1 to 21.5.0.

---
updated-dependencies:
- dependency-name: node
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/app/AlwaysOn.UI/Dockerfile

@@ -1,5 +1,5 @@
 # Create build environment
-FROM node:19.8.1 as build-env
+FROM node:21.5.0 as build-env
 
 WORKDIR /app
 COPY . ./