examples/tests/abort.py: remove default_params

Commit 72f9bb10 removed default_params, but it was not reflected on
examples/tests/abort.py example tests.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

examples/tests/abort.py

@@ -14,7 +14,7 @@ class AbortTest(Test):
     :avocado: tags=failure_expected
     """
 
-    default_params = {'timeout': 2.0}
+    timeout = 2.0
 
     def test(self):
         os.abort()