Fix config usage test

Author: huitema

picoquictest/config_usage_ref.txt

@@ -14,7 +14,7 @@ Picoquic options:
   -G cc_algorithm Use the specified congestion control algorithm: reno, cubic, bbr or fast. Defaults to bbr.
   -P number       Set the default spinbit policy
   -O number       Set the default lossbit policy
-  -M number       Multipath option: none(0), full(1), simple(2), both(3), unique(4), all (7)
+  -M number       Multipath option: none(0), full(1), simple(2), both(3)
   -e if           Send on interface (default: -1)
   -C cipher_suite_id specify cipher suite (e.g. -C 20 = chacha20)
   -i per-text-lb-spec See documentation for LB compatible CID configuration