patch 8.2.3961: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/spellfile.c b/src/spellfile.c
index 03da272..dc6647a 100644
--- a/src/spellfile.c
+++ b/src/spellfile.c
@@ -5963,7 +5963,7 @@
     }
 
     if (incount <= 0)
-	emsg(_(e_invarg));	// need at least output and input names
+	emsg(_(e_invalid_argument));	// need at least output and input names
     else if (vim_strchr(gettail(wfname), '_') != NULL)
 	emsg(_("E751: Output file name must not have region name"));
     else if (incount > MAXREGIONS)