Revert "Use :redrawstatus rather than &ro = &ro"

Turns out :redrawstatus is a lot more aggressive and can prevent seeing
Fugitive output.

This reverts commit 6ad15506cc.

References: https://github.com/tpope/vim-fugitive/issues/1180

autoload/fugitive.vim

@@ -4122,7 +4122,8 @@ function! s:DoAutocmdChanged(dir) abort
     exe s:DoAutocmd('User FugitiveChanged')
   finally
     unlet! g:fugitive_event g:fugitive_result
-    redrawstatus
+    " Force statusline reload with the buffer's Git dir
+    let &l:ro = &l:ro
   endtry
   return ''
 endfunction