widget.repaint does not overuse the scroll buffer

The `CSI 2 J` sequence stores screen contents in the scroll buffer in modern terminals.
In this case, this is unnecessary operation.

Author: YO4

lib/ruby_installer/runtime/console_ui.rb

@@ -161,7 +161,7 @@ def repaint(width: @con.winsize[1], height: @con.winsize[0])
           line += "\n"
           slines << []
         end
-        @con.write "\e[1;1H" "\e[2J"
+        @con.write "\e[H" "\e[J"
         print "#{headline}"
         print @con.cursor.last == 0 ? line.chomp : "\n#{line.chomp}"
         @slines = slines