Drop support for Python 3.5 (#4675)

Python 3.5 EOL was on 2020-09-30.

stdlib/3/http/client.pyi

@@ -156,18 +156,15 @@ class HTTPConnection:
             timeout: Optional[float] = ...,
             source_address: Optional[Tuple[str, int]] = ...,
         ) -> None: ...
-    if sys.version_info >= (3, 6):
-        def request(
-            self,
-            method: str,
-            url: str,
-            body: Optional[_DataType] = ...,
-            headers: Mapping[str, str] = ...,
-            *,
-            encode_chunked: bool = ...,
-        ) -> None: ...
-    else:
-        def request(self, method: str, url: str, body: Optional[_DataType] = ..., headers: Mapping[str, str] = ...) -> None: ...
+    def request(
+        self,
+        method: str,
+        url: str,
+        body: Optional[_DataType] = ...,
+        headers: Mapping[str, str] = ...,
+        *,
+        encode_chunked: bool = ...,
+    ) -> None: ...
     def getresponse(self) -> HTTPResponse: ...
     def set_debuglevel(self, level: int) -> None: ...
     def set_tunnel(self, host: str, port: Optional[int] = ..., headers: Optional[Mapping[str, str]] = ...) -> None: ...
@@ -175,10 +172,7 @@ class HTTPConnection:
     def close(self) -> None: ...
     def putrequest(self, method: str, url: str, skip_host: bool = ..., skip_accept_encoding: bool = ...) -> None: ...
     def putheader(self, header: str, *argument: str) -> None: ...
-    if sys.version_info >= (3, 6):
-        def endheaders(self, message_body: Optional[_DataType] = ..., *, encode_chunked: bool = ...) -> None: ...
-    else:
-        def endheaders(self, message_body: Optional[_DataType] = ...) -> None: ...
+    def endheaders(self, message_body: Optional[_DataType] = ..., *, encode_chunked: bool = ...) -> None: ...
     def send(self, data: _DataType) -> None: ...
 
 class HTTPSConnection(HTTPConnection):

stdlib/3/http/cookiejar.pyi

@@ -1,11 +1,9 @@
 import sys
 from http.client import HTTPResponse
+from os import PathLike
 from typing import Dict, Iterable, Iterator, Optional, Sequence, Tuple, TypeVar, Union, overload
 from urllib.request import Request
 
-if sys.version_info >= (3, 6):
-    from os import PathLike
-
 _T = TypeVar("_T")
 
 class LoadError(OSError): ...