Remove ev_timer_again calls

The documentation says about this function:

    If the timer is started but non-repeating, stop it (as if it timed out).

The timers are non-repeating, so we don't want this call.

https://linux.die.net/man/3/ev

include/amqpcpp/libev.h

@@ -271,9 +271,6 @@ private:
             // reset the timer to trigger again later
             ev_timer_set(&_timer, std::min(_next, _expire) - now, 0.0);
             
-            // restart the timer
-            ev_timer_again(_loop, &_timer);
-            
             // and because the timer is running again, we restore the refcounter
             ev_unref(_loop);
         }
@@ -368,9 +365,6 @@ private:
             // find the earliest thing that expires
             ev_timer_set(&_timer, std::min(_next, _expire) - now, 0.0);
             
-            // restart the timer
-            ev_timer_again(_loop, &_timer);
-            
             // expose the accepted interval
             return _timeout;
         }