Fix wrong documentation of PROXY_MEDIA, thanks bugzbunny

deploy/env.prod.sample

@@ -177,7 +177,7 @@ AWS_STORAGE_BUCKET_NAME=
 # AWS_S3_ENDPOINT_URL=
 
 # If you want to serve media directly from your S3 bucket rather than through a proxy,
-# set this to true
+# set this to false
 # PROXY_MEDIA=false
 
 # If you are using Amazon S3 to serve media directly, you will need to specify your region