fix: Missing slots attributes, wrong variable type, duplicate http methods

[Readeem]

Summary

I was just checking new update changes and I've noticed these small issues I fixed here in this PR.

What was fixed:

• Removed duplicated methods in HTTPClient class (might be breaking change but I don't think so, these weren't used)
• Fixed missed stacklevel parameter in warn_deprecated function call inside deprecated decorator in utils
• Fixed typehint in ConnectionState._polls incorrectly specified as Guild instead of Poll
• Fixed missing __slots__ attributes in RawReactionClearEmojiEvent class
• Fixed missing __slots__ attributes in RawMessagePollVoteEvent class
• Fixed default_sort_order variable type being int instead of typehinted SortOrder enum in ForumChannel class

I tested every fix, including checking type of default_sort_order variable. If there's something wrong with duplicated method removals in HTTPClient class, I can revert these changes.

Information

• [x] This PR fixes an issue.
• [ ] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed).
• [ ] This PR is not a code change (e.g. documentation, README, typehinting, examples, ...).

Checklist

• [x] I have searched the open pull requests for duplicates.
• [x] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
• [ ] If type: ignore comments were used, a comment is also left explaining why.
• [x] I have updated the changelog to include these changes.

[Lulalaby]

that definitely needs a changelog u can skip changelog for the first change tho

[Readeem]

Ready to be merged