Update README to list 9.6 properly (copy #2665)

[mergify]

This is an automatic copy of pull request #2665 done by Mergify.
Cherry-pick of cb331a8 has failed:

On branch mergify/copy/1.8/pr-2665
Your branch is up to date with 'origin/1.8'.

You are currently cherry-picking commit cb331a852.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .ci/cabal.project.local
	new file:   .ci/find_cabal_bin.sh
	modified:   .ci/gitlab/test.yml
	new file:   .ci/stack-9.6.yaml
	modified:   clash-cores/clash-cores.cabal

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/ci.yml
	both modified:   README.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com