Fix lint.

Author: zxybazh

python/tvm/meta_schedule/tune.py

@@ -591,7 +591,6 @@ def tune_relay(
             ):
                 if backend == "graph":
                     return relay_build(mod, target=target, params=params)
-                elif backend == "vm":
+                if backend == "vm":
                     return relay.vm.compile(mod, target=target, params=params)
-                else:
-                    raise ValueError(f"Backend {backend} not supported in ApplyHistoryBest!")
+                raise ValueError(f"Backend {backend} not supported in ApplyHistoryBest!")