fix: progress use vim.lsp.get_client_by_id

[armed]

Some language servers are not in active list until initialization is done.
For example clojure_lsp sends $/progress messages and activates itself (i.e. becomes available as active client) only when initialization is complete. In this case get_active_clients returns empty table. But get_client_by_id returns clojure client.

This PR replaces vim.lsp.get_active_clients with vim.lsp.get_client_by_id in progress handler.

[folke]

thanks!