patch 8.2.3985: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/os_amiga.c b/src/os_amiga.c
index 5bf088b..e9d6221 100644
--- a/src/os_amiga.c
+++ b/src/os_amiga.c
@@ -1256,7 +1256,7 @@
     if (close_win)
     {
 	// if Vim opened a window: Executing a shell may cause crashes
-	emsg(_("E360: Cannot execute shell with -f option"));
+	emsg(_(e_cannot_execute_shell_with_f_option));
 	return -1;
     }