Remove Python 3.7 support (#8361)

Closes #7803
Authored by: bashonly

yt_dlp/compat/functools.py

@@ -10,17 +10,3 @@ try:
     cache  # >= 3.9
 except NameError:
     cache = lru_cache(maxsize=None)
-
-try:
-    cached_property  # >= 3.8
-except NameError:
-    class cached_property:
-        def __init__(self, func):
-            update_wrapper(self, func)
-            self.func = func
-
-        def __get__(self, instance, _):
-            if instance is None:
-                return self
-            setattr(instance, self.func.__name__, self.func(instance))
-            return getattr(instance, self.func.__name__)