tests: speed up two slow tests

These were the most expansive tests, each taking more than 5min.
This should bring them back below 1min.

* tests/core/parity.test: Do not run through valgrind.
* tests/python/toweak.py: Remove one very long case.

tests/core/parity.test

@@ -1,6 +1,6 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2016 Laboratoire de Recherche et Développement
+# Copyright (C) 2016, 2017 Laboratoire de Recherche et Développement
 # de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -21,5 +21,5 @@
 
 . ./defs
 set -e
-
-run 0 ../parity
+# Do not run through valgrind, this takes too long.
+../parity

tests/python/toweak.py

@@ -21,7 +21,6 @@ import spot
 
 phi1 = """GFb
 X(!b | GF!a)
-!a U X(b | GF!b)
 GFa
 G(a M b)
 (!a | b) & GFb