Remove some def-style comments

They are mostly redundant with the method signature and don't look great when rendered.

Still remaining on nodes. I will improve docs for them in a separate PR

Author: Earlopain

templates/lib/prism/dispatcher.rb.erb

@@ -41,16 +41,12 @@ module Prism
     end
 
     # Register a listener for one or more events.
-    #
-    # def register: (Listener, *Symbol) -> void
     def register(listener, *events)
       register_events(listener, events)
     end
 
     # Register all public methods of a listener that match the pattern
     # `on_<node_name>_(enter|leave)`.
-    #
-    # def register_public_methods: (Listener) -> void
     def register_public_methods(listener)
       register_events(listener, listener.public_methods(false).grep(/\Aon_.+_(?:enter|leave)\z/))
     end
@@ -61,13 +57,9 @@ module Prism
     end
 
     # Walks `root` dispatching events to all registered listeners.
-    #
-    # def dispatch: (Node) -> void
     alias dispatch visit
 
     # Dispatches a single event for `node` to all registered listeners.
-    #
-    # def dispatch_once: (Node) -> void
     def dispatch_once(node)
       node.accept(DispatchOnce.new(listeners))
     end