Add missing BufWinEnter
Add missing BufWinEnter

`autocmd BufWinEnter * call ruby_hl_lvar#redraw()` exists in fd52ba13f1b5fee2a4413de9704ef91ea3ffdfc4, but it has been removed in 9b5d2c6d1d5a2d4331d36088611fa6cf1b648b98. I guess it was forgotten, so I restored it.

todesking/ruby_hl_lvar.vim