contrib(config): Update receiver S3 config

Using /dev/null file is not needed anymore.

Signed-off-by: Michal Rostecki <vadorovsky@gmail.com>

Author: vadorovsky

contrib/config/receiver-s3.yaml

@@ -2,8 +2,6 @@ input:
   address: 0.0.0.0
   port: 8081
 output:
-  file:
-    path: /dev/null
   plugins:
     s3:
       region: eu-west-1