build: bump httpx/respx dependencies

[namsnath]

• Pins httpx/respx to current major versions (<1.0.0)
• Will allow users to update their dependencies without us having to keep up
• Fixes broken tests due to latest httpx changes
• Removes respx dependency from fastapi install
  • fastapi has no dependency on respx
  • We only use respx in tests
• Bump version to 0.28.1

Summary of change

(A few sentences about this PR)

Related issues

• Link to issue1 here
• Link to issue1 here

Test Plan

(Write your test plan here. If you changed any code, please provide us with clear instructions on how you verified your changes work. Bonus points for screenshots and videos!)

Documentation changes

(If relevant, please create a PR in our docs repo, or create a checklist here highlighting the necessary changes)

Checklist for important updates

• Changelog has been updated
• coreDriverInterfaceSupported.json file has been updated (if needed)
  • Along with the associated array in supertokens_python/constants.py
• frontendDriverInterfaceSupported.json file has been updated (if needed)
• Changes to the version if needed
  • In setup.py
  • In supertokens_python/constants.py
• Had installed and ran the pre-commit hook
• Issue this PR against the latest non released version branch.
  • To know which one it is, run find the latest released tag (git tag) in the format vX.Y.Z, and then find the latest branch (git branch --all) whose X.Y is greater than the latest released tag.
  • If no such branch exists, then create one from the latest released branch.
• If have added a new web framework, update the supertokens_python/utils.py file to include that in the FRAMEWORKS variable
• If added a new recipe that has a User type with extra info, then be sure to change the User type in supertokens_python/types.py
• Make sure that syncio / asyncio functions are consistent.
• If access token structure has changed
  • Modified test in tests/sessions/test_access_token_version.py to account for any new claims that are optional or omitted by the core

Remaining TODOs for this PR

• Item1
• Item2