[PR #6857/1e8c40fe backport][3.9] Stop installing cchardet speedup under >Python 3.9

[patchback]

This is a backport of PR #6857 as merged into master (1e8c40f).

What do these changes do?

cchardet stopped being maintained a while ago so this patch removes
it from the speedups extra to keep it helpful. It also makes the
same adjustment in the CI under the most recent CPython versions to
keep the testing going.

Are there changes in behavior for the user?

pip install aiohttp[speedups] will only request cchardet under CPython < 3.10

Related issue number

• cchardet seems to be obsolete, charset_normalizer as an alternative #6819 (comment)
• Support Python 3.10 PyYoshi/cChardet#77

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."