Fix default hostname for Beta Cluster (#31)

Bug: https://phabricator.wikimedia.org/T282459

.env

@@ -30,4 +30,4 @@ APP_LOG_RECIPIENT_2=admin2@example.org
 APP_LOG_SUBJECT="[Wikimedia OCR]"
 
 # Comma-separated list of the host names (without protocols) of where images are stored.
-APP_IMAGE_HOSTS=upload.wikimedia.org,upload.beta.wmflabs.org
+APP_IMAGE_HOSTS=upload.wikimedia.org,upload.wikimedia.beta.wmflabs.org