chore: remove the legacy video demo app (#1272)

As part of #1194, this application was merged with the one we use for
internal testing (react-dogfood). As we don't want to maintain this
codebase anymore, this PR removes the app's code.
We know some customers might have looked into it and that is why the
`react-video-demo` directory stays in the React sample apps. The Readme
is updated with a hint to look at the React Dogfood app instead.

package.json

@@ -28,7 +28,6 @@
     "build:react:deps": "yarn build:client && yarn build:styling && yarn build:react:bindings && yarn build:react:sdk",
     "build:react-native:deps": "yarn build:client && yarn build:react:bindings && yarn build:react-native:sdk",
     "build:vercel": "yarn build:react:deps && yarn build:react:dogfood",
-    "build:react:video-demo": "yarn build:react:deps && yarn workspace @stream-io/react-video-demo run build:website",
     "start:egress": "yarn workspace @stream-io/egress-composite start",
     "build:egress": "yarn workspace @stream-io/egress-composite build",
     "build:all": "yarn workspaces foreach -v --topological-dev run build",

sample-apps/react/react-video-demo/README.md

@@ -1,4 +1,3 @@
 ## @stream-io/react-video-demo
 
-Preview: https://staging.getstream.io/video/demos/
-Production: https://getstream.io/video/demos/
+This application has been merged with [react-dogfood](../react-dogfood) and is no longer maintained.