Corrected a command line typo (angular#1918)

DavidBowdoin · davideast · commit d6f59c782cd7 · 2018-10-17T07:26:36.000-06:00
diff --git a/docs/deploying-angularfire-to-firebase.md b/docs/deploying-angularfire-to-firebase.md
@@ -7,7 +7,7 @@ Make sure to add your production firebase configuraiton to the src/environments/
 
 ```bash
 # build the angular project, creates a dist folder in your directory
-ng build -prod
+ng build --prod
 ```
 
 ### 1. Initializing a Firebase project
