对齐 Gitea 缓存维护用例与已退役 smoke job 的 job 数量

- test_gitea_cache_maintenance.py 中两处硬编码的缓存导出/合并分组数 6 改为按 maintainer RUST_JOB_IDS 动态取值，避免新增或退役 CI job 时用例与实现脱节

scripts/test_gitea_cache_maintenance.py

@@ -340,7 +340,7 @@ class GiteaCacheMaintenanceTest(unittest.TestCase):
         instance, run, jobs, artifacts = self.source_fixture()
         result = self.select_source(instance)
         self.assertEqual(result["run_id"], 44)
-        self.assertEqual(len(result["exports"]), 6)
+        self.assertEqual(len(result["exports"]), len(maintenance_module.RUST_JOB_IDS))
         self.assertEqual({item["size_in_bytes"] for item in result["exports"]}, {10})
         run["event"] = "pull_request"
         self.assertIsNone(self.select_source(instance))
@@ -421,7 +421,7 @@ class GiteaCacheMaintenanceTest(unittest.TestCase):
         instance.docker = docker
         instance.api.download = lambda path, destination, expected_size: destination.write_bytes(b"download")
         def merge(inputs, output, **kwargs):
-            self.assertEqual(len(inputs), 6)
+            self.assertEqual(len(inputs), len(maintenance_module.RUST_JOB_IDS))
             self.assertEqual(kwargs["expected_inherited_source_sha"], "b" * 40)
             output.mkdir()
             (output / "objects").mkdir()