core: cleanup/sort imports according to ruff check --select I

my/core/utils/concurrent.py

@@ -1,10 +1,9 @@
-from concurrent.futures import Future, Executor
 import sys
-from typing import Any, Callable, Optional, TypeVar, TYPE_CHECKING
+from concurrent.futures import Executor, Future
+from typing import TYPE_CHECKING, Any, Callable, Optional, TypeVar
 
 from ..compat import ParamSpec
 
-
 _P = ParamSpec('_P')
 _T = TypeVar('_T')
 
@@ -15,6 +14,7 @@ class DummyExecutor(Executor):
     This is useful if you're already using Executor for parallelising,
      but also want to provide an option to run the code serially (e.g. for debugging)
     """
+
     def __init__(self, max_workers: Optional[int] = 1) -> None:
         self._shutdown = False
         self._max_workers = max_workers