Remove .htaccess creation code

As discussed in https://github.com/owncloud/core/pull/7471:

1. We're maintaining the same code twice which leads inevitably to problems as this one. The createHtaccess routine is only used to use the correct paths to the 404 and 403 document.
2. Updating the ownCloud instance as described in our documentation (`Delete everything from your ownCloud installation directory, except data and config.`) will break the links to the ErrorDocuments anyways and show the default error handlers if ownCloud is not installed in the root directory.