Revert Amazon S3 part from 075e8d8e8658913e1c5b8869f3e457fa6db2d847

Amazon S3 part broken and untested, reverting.

This is a partial revert of 075e8d8e8658913e1c5b8869f3e457fa6db2d847 which only reverts the amazons3.php file.

Fixes https://github.com/owncloud/core/issues/11714