deps: upgrade fastboot to v4

Author: ignace

package.json

@@ -57,7 +57,7 @@
     "ember-cli-deploy": "^1.0.2",
     "ember-cli-deploy-build": "^2.0.0",
     "ember-cli-deploy-prember-algolia": "^1.0.1",
-    "ember-cli-fastboot": "^3.0.0",
+    "ember-cli-fastboot": "^4.1.2",
     "ember-cli-htmlbars": "^6.0.1",
     "ember-cli-inject-live-reload": "^2.1.0",
     "ember-cli-netlify": "^0.4.1",