Remove previously deprecated cached_property (home-assistant#146478)

Co-authored-by: Robert Resch <[email protected]>

Author: gjohansson-ST

homeassistant/backports/functools.py

@@ -25,12 +25,6 @@ class ObsoleteImportMatch:
             constant=re.compile(r"^cached_property$"),
         ),
     ],
-    "homeassistant.backports.functools": [
-        ObsoleteImportMatch(
-            reason="replaced by propcache.api.cached_property",
-            constant=re.compile(r"^cached_property$"),
-        ),
-    ],
     "homeassistant.components.light": [
         ObsoleteImportMatch(
             reason="replaced by ColorMode enum",