vim-patch:8.0.1216: tabline is not always updated for :file command

Problem:    Tabline is not always updated for :file command. (Norio Takagi)
Solution:   Set redraw_tabline. (Hirohito Higashi)
6ce6504808

src/nvim/ex_cmds.c

@@ -1598,6 +1598,7 @@ void ex_file(exarg_T *eap)
     // print full file name if :cd used
     fileinfo(false, false, eap->forceit);
   }
+  redraw_tabline = true;
 }
 
 /*