Preserve Python 3.9 compatibility
diff --git a/modules/shared.py b/modules/shared.py
index fa080458567..e53b1e113c7 100644
--- a/modules/shared.py
+++ b/modules/shared.py
@@ -15,6 +15,7 @@
 from modules import localization, script_loading, errors, ui_components, shared_items, cmd_args
 from modules.paths_internal import models_path, script_path, data_path, sd_configs_path, sd_default_config, sd_model_file, default_sd_model_file, extensions_dir, extensions_builtin_dir  # noqa: F401
 from ldm.models.diffusion.ddpm import LatentDiffusion
+from typing import Optional
 
 demo = None
 
@@ -113,7 +114,7 @@ class State:
     time_start = None
     server_start = None
     _server_command_signal = threading.Event()
-    _server_command: str | None = None
+    _server_command: Optional[str] = None
 
     @property
     def need_restart(self) -> bool:
@@ -131,14 +132,14 @@ def server_command(self):
         return self._server_command
 
     @server_command.setter
-    def server_command(self, value: str | None) -> None:
+    def server_command(self, value: Optional[str]) -> None:
         """
         Set the server command to `value` and signal that it's been set.
         """
         self._server_command = value
         self._server_command_signal.set()
 
-    def wait_for_server_command(self, timeout: float | None = None) -> str | None:
+    def wait_for_server_command(self, timeout: Optional[float] = None) -> Optional[str]:
         """
         Wait for server command to get set; return and clear the value and signal.
         """

**Describe what this pull request is trying to achieve.**

The dev branch currently does not launch due to a TypeError in Python 3.9 environments (e.g. Colab Pro, Paperspace Gradient). This is because of newer Optional type syntax usage in `shared.py` added by #10458. This PR changes three lines to use `typing.Optional` instead to preserve backwards compatibility.

**Additional notes and description of your changes**

It's a minor syntax change and I've tested launch and restarts to be working but please ensure everything is correct as I'm not really a programmer. Thank you.

**Environment this was tested in**
 - OS: Linux (Paperspace Gradient)
 - Browser: Firefox
 - Graphics card: Nvidia RTX A4000