Close #4579 - Support numhl highlights for vim >= 8.2.3874

In #2637, support for numhl highlights was added for nvim.

In the meantime, vim added support for numhl highlights in patch 8.2.3874.

This patch allows numhl highlights to be enabled in ALE for vim >= 8.2.3874 too.

autoload/ale/sign.vim

@@ -87,7 +87,7 @@ execute 'sign define ALEInfoSign text=' . s:EscapeSignText(g:ale_sign_info)
 \   . ' texthl=ALEInfoSign linehl=ALEInfoLine'
 sign define ALEDummySign text=\  texthl=SignColumn
 
-if g:ale_sign_highlight_linenrs && has('nvim-0.3.2')
+if g:ale_sign_highlight_linenrs && (has('nvim-0.3.2') || has('patch-8.2.3874'))
     if !hlexists('ALEErrorSignLineNr')
         highlight link ALEErrorSignLineNr CursorLineNr
     endif