Remove Settings.Global.TCP_DEFAULT_INIT_RWND on CS

TCP_DEFAULT_INIT_RWND setting has never been set before, CS
always read the tcp receive window size from
net.tcp.default_init_rwnd then set to net.tcp_def_init_rwnd.
Thus, remove the unnecessary setting from CS, and the property
doesn't need to set either. Because aosp/1639922 migrate the
properties, the default value has been set to kernel already.

Bug: 182538166
Test: atest FrameworksNetTests
Change-Id: I13e175ab4dea72446af7df4a25e307e5934fa813