chore: stop pinning the concurrently dep to a precise version (#1262)

Use the recent improvement of lostpebble/generate-package-json-webpack-plugin#49 to propagate
a caret version of the concurrently dep in the released package.

Fixes #1248

Author: pcorpet

apps/generator-cli/webpack.config.js

@@ -33,6 +33,7 @@ module.exports = composePlugins(
         'reflect-metadata': '',
         '@nuxtjs/opencollective': '',
         axios: '^',
+        concurrently: '^',
       },
     };