build: Drop the @edx/reactifex package

Remove @edx/reactifex package from devDependencies as it is no longer
needed. Translation extraction functionality has been verified to work
correctly without this dependency.  We don't need it in the template
application.

Author: feanil

package-lock.json

@@ -57,7 +57,6 @@
   },
   "devDependencies": {
     "@edx/browserslist-config": "^1.1.1",
-    "@edx/reactifex": "^2.1.1",
     "@openedx/frontend-build": "14.6.2",
     "glob": "7.2.3",
     "husky": "7.0.4",