Add missing parenthesis

Author: elia

lib/solid_queue/processes/process_pruned_error.rb

@@ -4,7 +4,7 @@ module SolidQueue
   module Processes
     class ProcessPrunedError < RuntimeError
       def initialize(last_heartbeat_at)
-        super("Process was found dead and pruned (last heartbeat at: #{last_heartbeat_at}")
+        super("Process was found dead and pruned (last heartbeat at: #{last_heartbeat_at})")
       end
     end
   end