Clean up several version-dependent modules (#6885)

stdlib/asyncio/exceptions.pyi

@@ -1,14 +1,13 @@
-import sys
+class CancelledError(BaseException): ...
+class TimeoutError(Exception): ...
+class InvalidStateError(Exception): ...
+class SendfileNotAvailableError(RuntimeError): ...
 
-if sys.version_info >= (3, 8):
-    class CancelledError(BaseException): ...
-    class TimeoutError(Exception): ...
-    class InvalidStateError(Exception): ...
-    class SendfileNotAvailableError(RuntimeError): ...
-    class IncompleteReadError(EOFError):
-        expected: int | None
-        partial: bytes
-        def __init__(self, partial: bytes, expected: int | None) -> None: ...
-    class LimitOverrunError(Exception):
-        consumed: int
-        def __init__(self, message: str, consumed: int) -> None: ...
+class IncompleteReadError(EOFError):
+    expected: int | None
+    partial: bytes
+    def __init__(self, partial: bytes, expected: int | None) -> None: ...
+
+class LimitOverrunError(Exception):
+    consumed: int
+    def __init__(self, message: str, consumed: int) -> None: ...