fix: Comment out comment explaining readonly basic auth creds (#2302)

This causes an error if `.env.template` is copied directly into `.env`.

Author: joshlarson

.env.template

@@ -28,6 +28,6 @@ REDIS_STANDALONE=true
 # BASIC_AUTH_PASSWORD=
 
 # These credentials control access to read-only resources, such as the Live
-Dashboard, the admin page, and features under the /preview path.
+# Dashboard, the admin page, and features under the /preview path.
 # BASIC_AUTH_READONLY_USERNAME=
 # BASIC_AUTH_READONLY_PASSWORD=