Adjust wording a bit

**Before:**
> Your PHP version (5.4.16) is no longer supported by PHP. We encourage you to upgrade your PHP version to take advantage of performance and security updates provided by PHP.

**After:**
> You are currently running PHP 5.4.0. We encourage you to upgrade your PHP version to take advantage of performance and security updates provided by the PHP Group as soon as your distribution supports it.

Fixes https://github.com/owncloud/enterprise/issues/1170