Fix rpi_camera setup hanging on initialization (#59316)

homeassistant/components/rpi_camera/camera.py

@@ -119,10 +119,13 @@ class RaspberryCamera(Camera):
             cmd_args.append("-a")
             cmd_args.append(str(device_info[CONF_OVERLAY_TIMESTAMP]))
 
-        with subprocess.Popen(
+        # The raspistill process started below must run "forever" in
+        # the background until killed when Home Assistant is stopped.
+        # Therefore it must not be wrapped with "with", since that
+        # waits for the subprocess to exit before continuing.
+        subprocess.Popen(  # pylint: disable=consider-using-with
             cmd_args, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT
-        ):
-            pass
+        )
 
     def camera_image(
         self, width: int | None = None, height: int | None = None