test_missing_obj_finder: correct bogus wants test

This test hasn't been doing what it says on the tin for a while, because
find_missing_objects doesn't take a store argument.

dulwich/tests/test_missing_obj_finder.py

@@ -104,7 +104,7 @@ class MOFLinearRepoTest(MissingObjectFinderTest):
         haves = [self.cmt(1).id]
         wants = [self.cmt(3).id, bogus_sha]
         self.assertRaises(KeyError, self.store.find_missing_objects,
-            self.store, haves, wants)
+            haves, wants)
 
     def test_no_changes(self):
         self.assertMissingMatch([self.cmt(3).id], [self.cmt(3).id], [])