Update backup_and_upload_to_s3.php

In the following code snippet, each object in the bucket must be submitted as an array; otherwise, you get 'Validation errors: [Objects][key] must be of type object' 

i.e. 

.....
.....
'Objects' => array(
    		    array( 'key' => $file['Key'] )
    		   )
......
......