[ruby/irb] fixes https://github.com/ruby/irb/pull/524

(https://github.com/ruby/irb/pull/696)

https://github.com/ruby/irb/commit/59bcc07def

lib/irb.rb

@@ -535,7 +535,6 @@ module IRB
             prompt_i = @context.prompt_i.nil? ? "" : @context.prompt_i
             ind = prompt(prompt_i, ltype, indent, line_no)[/.*\z/].size +
               indent * 2 - p.size
-            ind += 2 if continue
             @context.io.prompt = p + " " * ind if ind > 0
           end
         end