event/SocketMonitor: add "noexcept"

src/lib/nfs/Connection.cxx

@@ -446,7 +446,7 @@ NfsConnection::Service(unsigned flags)
 }
 
 bool
-NfsConnection::OnSocketReady(unsigned flags)
+NfsConnection::OnSocketReady(unsigned flags) noexcept
 {
 	assert(GetEventLoop().IsInside());
 	assert(deferred_close.empty());

src/lib/nfs/Connection.hxx

@@ -230,7 +230,7 @@ private:
 	int Service(unsigned flags);
 
 	/* virtual methods from SocketMonitor */
-	virtual bool OnSocketReady(unsigned flags) override;
+	bool OnSocketReady(unsigned flags) noexcept override;
 
 	/* callback for #mount_timeout_event */
 	void OnMountTimeout();