Remove default radix theme (#2403)

reflex/app.py

@@ -46,7 +46,6 @@ from reflex.components.core.client_side_routing import (
     Default404Page,
     wait_for_client_redirect,
 )
-from reflex.components.radix import themes
 from reflex.config import get_config
 from reflex.event import Event, EventHandler, EventSpec
 from reflex.middleware import HydrateMiddleware, Middleware
@@ -132,11 +131,11 @@ class App(Base):
         Union[Component, ComponentCallable]
     ] = default_overlay_component
 
-    # Background tasks that are currently running
+    # Background tasks that are currently running.
     background_tasks: Set[asyncio.Task] = set()
 
-    # The radix theme for the entire app
-    theme: Optional[Component] = themes.theme(accent_color="blue")
+    # The radix theme for the entire app.
+    theme: Optional[Component]
 
     def __init__(self, *args, **kwargs):
         """Initialize the app.