Remove unnecessary call to @argv.delete

Author: justin808

lib/webpacker/webpack_runner.rb

@@ -28,7 +28,6 @@ def run
 
       if @argv.delete "--debug-webpacker"
         cmd = ["node", "--inspect-brk"] + cmd
-        @argv.delete "--debug-webpacker"
       end
 
       if @argv.delete "--trace-deprecation"