Remove 0x2 bit from SETTINGS_FLOW_CONTROL_OPTIONS.

It controls the connection window, but there is already a mechanism for
that in WINDOW_UPDATE with stream 0 and the END_FLOW_CONTROL flag,
therefore it is redundant.

Issue #88.
Discussion: http://lists.w3.org/Archives/Public/ietf-http-wg/2013AprJun/0709.html