[web] stop adding an Expires header with all responses
As per RFC 1945 (HTTP 1.0):
If the date given is equal to or earlier than the value of the Date
header, the recipient must not cache the enclosed entity.
As per RFC 7234 (HTTP 1.1 Caching):
If a response includes a Cache-Control field with the max-age
directive (Section 5.2.2.8), a recipient MUST ignore the Expires
field.
Bottom line, the Expires header is now handled wherever the
Cache-Control is handled: inside cache managers.