Fix Platform.sh redirects for "Using Composer" page (#242)

Fixed #241

Author: mglaman

.platform/routes.yaml

@@ -8,7 +8,7 @@ https://{default}/:
 
       # Outline change
       "/commerce2/developer-guide/getting-started": {"to": "/commerce2/getting-started"}
-      "/commerce2/getting-started/using-composer": {"to": "/commerce2/developer-guide/install-update/using-composer"}
+      "/commerce2/developer-guide/install-update/using-composer": {"to": "/commerce2/getting-started/using-composer"}
       "/commerce2/getting-started/install": {"to": "/developer-guide/install-update/installation"}
       "/commerce2/getting-started/update": {"to": "/developer-guide/install-update/updating"}
       "/commerce2/getting-started/contributing": {"to": "/commerce2/developer-guide/contributing"}