patch 8.2.3986: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/gui_x11.c b/src/gui_x11.c
index 7828ab7..31363a8 100644
--- a/src/gui_x11.c
+++ b/src/gui_x11.c
@@ -1463,7 +1463,7 @@
     }
 
     if (gui.color_approx)
-	emsg(_("Vim E458: Cannot allocate colormap entry, some colors may be incorrect"));
+	emsg(_(e_cannot_allocate_colormap_entry_some_colors_may_be_incorrect));
 
 #ifdef FEAT_BEVAL_GUI
     gui_init_tooltip_font();