Remove a couple Python 2 __nonzero__ definitions

It's called __bool__ in Python 3.

src/_pytest/mark/evaluate.py

@@ -38,8 +38,6 @@ class MarkEvaluator:
         # don't cache here to prevent staleness
         return bool(self._get_marks())
 
-    __nonzero__ = __bool__
-
     def wasvalid(self):
         return not hasattr(self, "exc")
 

testing/test_assertrewrite.py

@@ -640,10 +640,10 @@ class TestAssertionRewrite:
 
         assert getmsg(f) == "assert 5 <= 4"
 
-    def test_assert_raising_nonzero_in_comparison(self):
+    def test_assert_raising__bool__in_comparison(self):
         def f():
             class A:
-                def __nonzero__(self):
+                def __bool__(self):
                     raise ValueError(42)
 
                 def __lt__(self, other):