remove useless comments

Author: monkeyWzr

lib/ruby_lsp/listeners/completion.rb

@@ -569,7 +569,6 @@ def complete_keyword_arguments(call_node, filter = nil)
           when ","
             arguments = call_node.arguments
             if arguments
-              # TODO: most possible position
               nearest_argument = arguments.arguments.flat_map do
                 _1.is_a?(Prism::KeywordHashNode) ? _1.elements : _1
               end.find do |argument|