refactor(lsp): remove usage of deprecated function (#16787)

(cherry picked from commit bb31d3f21a)

Co-authored-by: Gregory Anders <greg@gpanders.com>

runtime/lua/vim/lsp.lua

@@ -489,7 +489,8 @@ local function text_document_did_open_handler(bufnr, client)
     -- Protect against a race where the buffer disappears
     -- between `did_open_handler` and the scheduled function firing.
     if vim.api.nvim_buf_is_valid(bufnr) then
-      vim.lsp.diagnostic.redraw(bufnr, client.id)
+      local namespace = vim.lsp.diagnostic.get_namespace(client.id)
+      vim.diagnostic.show(namespace, bufnr)
     end
   end)
 end

runtime/lua/vim/lsp/diagnostic.lua

@@ -584,7 +584,7 @@ end
 
 --- Redraw diagnostics for the given buffer and client
 ---
----@deprecated Prefer |vim.diagnostic.redraw()|
+---@deprecated Prefer |vim.diagnostic.show()|
 ---
 --- This calls the "textDocument/publishDiagnostics" handler manually using
 --- the cached diagnostics already received from the server. This can be useful