Revert fix MultiDict typing with multidict-6.0.0 (#64733)

[mib1185]

Proposed change

This will revert #64733, since it has been fixed upstream with 6.0.1
https://github.com/aio-libs/multidict/releases/tag/v6.0.1

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[mib1185]

these errors are also related to multidict - but this time they occur only from 6.0.1, but not with 5.2.0 or 6.0.0 😕

Error: homeassistant/components/http/ban.py:120: error: No overload variant of "get" of "Mapping" matches argument type "str"  [call-overload]
homeassistant/components/http/ban.py:120: note: Possible overload variants:
homeassistant/components/http/ban.py:120: note:     def get(self, key: istr) -> Optional[str]
homeassistant/components/http/ban.py:120: note:     def [_T] get(self, istr, Union[str, _T]) -> Union[str, _T]
Error: homeassistant/helpers/config_entry_oauth2_flow.py:135: error: No overload variant of "get" of "Mapping" matches argument type "str"  [call-overload]
homeassistant/helpers/config_entry_oauth2_flow.py:135: note: Possible overload variants:
homeassistant/helpers/config_entry_oauth2_flow.py:135: note:     def get(self, key: istr) -> Optional[str]
homeassistant/helpers/config_entry_oauth2_flow.py:135: note:     def [_T] get(self, istr, Union[str, _T]) -> Union[str, _T]
Error: homeassistant/components/buienradar/camera.py:134: error: No overload variant of "get" of "Mapping" matches argument type "str"  [call-overload]
homeassistant/components/buienradar/camera.py:134: note: Possible overload variants:
homeassistant/components/buienradar/camera.py:134: note:     def get(self, key: istr) -> Optional[str]
homeassistant/components/buienradar/camera.py:134: note:     def [_T] get(self, istr, Union[str, _T]) -> Union[str, _T]
Found 3 errors in 3 files (checked 4578 source files)

[mib1185]

in aiohttp multidict has been pined down <6.0.0 since they observe also many issue with new version
aio-libs/aiohttp#6550