exec: small typo in log message

(cherry picked from commit 8a501f2be2860b1bfd0b9a3d1f63d85f4654fd01)
(cherry picked from commit d23c5d782aaef224e283766e8faeb9a1119bd279)

src/modules/exec/exec_hf.c

@@ -483,7 +483,7 @@ static int append_fixed_vars(struct sip_msg *msg, struct hf_wrapper **list)
 	} else {
 		if (!append_var(EV_OUSER, oparsed_uri.user.s, 
 					oparsed_uri.user.len, list)) {
-			LM_ERR("ppend_var OUSER failed\n");
+			LM_ERR("append_var OUSER failed\n");
 			goto error;
 		}
 	}