[Bugfix]fix_mulit_connector_bug (#3332)

### What this PR does / why we need it?
When using multi connector, the multi connector does not define
get_finished_count, which will cause the kv cache to be released
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: v0.11.0rc3
- vLLM main:
83f478bb19

---------

Signed-off-by: baxingpiaochong <771405853@qq.com>

tests/ut/kv_connector/test_mooncake_connector.py

@@ -673,10 +673,6 @@ class TestMooncakeConnectorSchedulerMatchedTokens(unittest.TestCase):
         self.assertEqual(meta.requests["req1"].remote_block_ids, [1, 2, 3])
         self.assertEqual(len(self.scheduler._reqs_need_recv), 0)
 
-    def test_get_finished_count(self):
-        count = self.scheduler.get_finished_count()
-        self.assertEqual(count, 2)
-
 
 class TestHelperFunctions(unittest.TestCase):