Revert "Restore memoize mistakenly removed in 7f412a16d72bad13b"

This reverts commit 29125cb1cc733b0aaf149bad538951ca7fa7c3b6.
Revert "Cleanup Octokit::Client#request"

This reverts commit 7f412a16d72bad13b1fcf386fc9ba2e5c5b73ea4.