UPDATE upstream copilot client version [use github action to automatically update]

[y9c]

• lastest version improve speed for some language (documented in vscode plugin)
• use github action to sync latest version from copilot.vim.

[zbirenbaum]

While I intentionally haven't been autoupdating it since on a few occasions it introduced problems due to bugs in the lsp server, I think Copilot has probably reached a point where it's more stable now, and if they are doing performance releases now it would probably be good to keep sync'd. Thanks for writing up an action for it!