Drop support for Python 3.7 (#11234)

CONTRIBUTING.md

@@ -279,11 +279,6 @@ new features to the Python type system. In general, new features can
 be used in typeshed as soon as the PEP has been accepted and implemented
 and most type checkers support the new feature.
 
-Accepted features that *cannot* yet be used in typeshed include:
-- [PEP 570](https://www.python.org/dev/peps/pep-0570/) (positional-only
-  arguments): see [#4972](https://github.com/python/typeshed/issues/4972),
-  use argument names prefixed with `__` instead
-
 The following features are partially supported:
 - [PEP 702](https://peps.python.org/pep-0702/) (`@deprecated()`)
   - For now, cannot be used in combination with other decorators
@@ -309,10 +304,6 @@ Features from the `typing` module that are not present in all
 supported Python 3 versions must be imported from `typing_extensions`
 instead in typeshed stubs. This currently affects:
 
-- `Final` and `@final` (new in Python 3.8)
-- `Literal` (new in Python 3.8)
-- `SupportsIndex` (new in Python 3.8)
-- `TypedDict` (new in Python 3.8)
 - `Concatenate` (new in Python 3.10)
 - `ParamSpec` (new in Python 3.10)
 - `TypeGuard` (new in Python 3.10)
@@ -320,10 +311,6 @@ instead in typeshed stubs. This currently affects:
 - `LiteralString` (new in Python 3.11)
 - `@deprecated` (new in Python 3.13; in the `warnings` module)
 
-Two exceptions are `Protocol` and `runtime_checkable`: although
-these were added in Python 3.8, they can be used in stubs regardless
-of Python version.
-
 Some type checkers implicitly promote the `bytearray` and
 `memoryview` types to `bytes`.
 [PEP 688](https://www.python.org/dev/peps/pep-0688/) removes