tests: Unmark unexpected successes

These tests are passing on 2.6.0.

test/filter.t

@@ -659,7 +659,6 @@ class TestBug1600(TestCase):
     def setUp(self):
         self.t = Task()
 
-    @unittest.expectedFailure
     def test_filter_plus_in_descriptions(self):
         """filter - description contains +"""
         self.t("add foobar1")

test/project.t

@@ -454,7 +454,6 @@ class TestBug1430(TestCase):
         self.assertEqual("home/garden\n", out)
 
 
-@unittest.expectedFailure
 class TestBug1617(TestCase):
     def setUp(self):
         """Executed before each test in the class"""

test/search.t

@@ -244,7 +244,6 @@ class Test1469(TestCase):
         self.assertNotIn('foo', out)
 
 
-@unittest.expectedFailure
 class TestBug1479(TestCase):
     def setUp(self):
         """Executed before each test in the class"""