perf: query fewer historical messages on reconnects (#5001)

Co-authored-by: Ruben Anders <ruben.anders@robotty.de>
Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

src/common/Channel.hpp

@@ -61,8 +61,6 @@ public:
     pajlada::Signals::Signal<const std::vector<MessagePtr> &> filledInMessages;
     pajlada::Signals::NoArgSignal destroyed;
     pajlada::Signals::NoArgSignal displayNameChanged;
-    /// Invoked when AbstractIrcServer::onReadConnected occurs
-    pajlada::Signals::NoArgSignal connected;
 
     Type getType() const;
     const QString &getName() const;