Fix `TopHits.searched_nodes` returning search residues instead of searched nodes

pyhmmer/plan7.pyx

@@ -6514,7 +6514,7 @@ cdef class TopHits:
         .. versionadded:: 0.5.0
 
         """
-        return self._pli.nres
+        return self._pli.nnodes
 
     @property
     def searched_sequences(self):

pyhmmer/tests/test_plan7/test_tophits.py

@@ -125,7 +125,7 @@ class TestTopHits(unittest.TestCase):
     def test_searched_nodes(self):
         empty = TopHits()
         self.assertEqual(empty.searched_nodes, 0)
-        self.assertEqual(self.hits.searched_nodes, 682583)
+        self.assertEqual(self.hits.searched_nodes, self.hmm.M)
 
     def test_searched_residues(self):
         empty = TopHits()