Use tagbar_iconchars not present in emoji (#807)

plugin/tagbar.vim

@@ -135,7 +135,7 @@ call s:setup_options()
 if !exists('g:tagbar_iconchars')
     if has('multi_byte') && has('unix') && &encoding ==# 'utf-8' &&
      \ (!exists('+termencoding') || empty(&termencoding) || &termencoding ==# 'utf-8')
-        let g:tagbar_iconchars = ['▶', '▼']
+        let g:tagbar_iconchars = ['▸', '▾']
     else
         let g:tagbar_iconchars = ['+', '-']
     endif