Remove bool argument from OnConnectionChangedCallback

We don't want to assert that implementation will have correct
implementation.

BUG: 24267885
Change-Id: I50b57de19253b32f1282820c2320ad366d0b5ffd
Reviewed-on: https://weave-review.googlesource.com/1099
Reviewed-by: Alex Vakulenko <avakulenko@google.com>
diff --git a/libweave/src/notification/xmpp_channel.cc b/libweave/src/notification/xmpp_channel.cc
index ce0c001..1acb679 100644
--- a/libweave/src/notification/xmpp_channel.cc
+++ b/libweave/src/notification/xmpp_channel.cc
@@ -457,7 +457,7 @@
   Restart();
 }
 
-void XmppChannel::OnConnectivityChanged(bool online) {
+void XmppChannel::OnConnectivityChanged() {
   if (state_ == XmppState::kNotStarted)
     return;