Remove unused code to old Visual Studio in `tasks/toolchains/visualcpp.rake`

tasks/toolchains/visualcpp.rake

@@ -54,16 +54,4 @@ MRuby::Toolchain.new(:visualcpp) do |conf, _params|
   end
 
   conf.file_separator = '\\'
-
-  # Unreliable detection and will result in invalid encoding errors for localized versions of Visual C++
-  # if require 'open3'
-  #   Open3.popen3 conf.cc.command do |_, _, e, _|
-  #     if /Version (\d{2})\.\d{2}\.\d{5}/ =~ e.gets && $1.to_i <= 17
-  #       m = "# VS2010/2012 support will be dropped after the next release! #"
-  #       h = "#" * m.length
-  #       puts h, m, h
-  #     end
-  #   end
-  # end
-
 end