nvim: Upgrade vim-plug

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

nvim/.local/share/nvim/site/autoload/plug.vim

@@ -251,7 +251,7 @@ endfunction
 
 function! plug#end()
   if !exists('g:plugs')
-    return s:err('Call plug#begin() first')
+    return s:err('plug#end() called without calling plug#begin() first')
   endif
 
   if exists('#PlugLOD')