chore(formatting): deprecation warning text for route handler classes (…

…#3559)

The deprecation warning is missing a space between "by" and "functional".

When printing to the screen, it would read a single work "byfunctional"

litestar/handlers/http_handlers/decorators.py

@@ -49,7 +49,7 @@
 class _SubclassWarningMixin:
     def __init_subclass__(cls, **kwargs: Any) -> None:
         warnings.warn(
-            "Semantic HTTP route handler classes are deprecated and will be replaced by"
+            "Semantic HTTP route handler classes are deprecated and will be replaced by "
             "functional decorators in Litestar 3.0.",
             category=DeprecationWarning,
             stacklevel=2,