build: Install typing_extensions only for python<3.8 (#220)

To mirror the changes from `aiohttp==~3.8`, which also install
`typing-extensions` only for Python 3.8-.

Author: q0w

pyproject.toml

@@ -121,7 +121,7 @@ isodate = "^0.6.0"
 openapi-core = ">=0.13.4,<0.13.7"
 pyrsistent = ">=0.16,<0.19"
 PyYAML = ">=5.1,<7.0"
-typing-extensions = ">=3.7,<5.0"
+typing-extensions = {python = "<3.8", version = ">=3.7,<5.0"}
 
 [tool.poetry.dev-dependencies]
 aioredis = {extras = ["hiredis"], version = "^2.0.0"}

src/rororo/annotations.py

@@ -13,9 +13,9 @@
 
 
 try:
-    from typing_extensions import Literal, Protocol, TypedDict
+    from typing import Literal, Protocol, TypedDict
 except ImportError:
-    from typing import Literal, Protocol, TypedDict  # type: ignore
+    from typing_extensions import Literal, Protocol, TypedDict  # type: ignore
 
 from aiohttp import web
 from aiohttp_middlewares.annotations import Handler