patch 8.2.4008: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 351ce82..9520998 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -2194,8 +2194,7 @@
 		else
 #endif
 		{
-		    semsg(_("E768: Swap file exists: %s (:silent! overrides)"),
-								    swapname);
+		    semsg(_(e_swap_file_exists_str_silent_overrides), swapname);
 		    vim_free(swapname);
 		    return FAIL;
 		}