lsp: remove popup No signature available. (#12915)

* lsp: remove popup No signature available.

 If no signatures. we shouldn't popup No signature available ..It will make noise when use
` api.nvim_command("autocmd CompleteDone <buffer> lua vim.lsp.buf.signature_help()")`

* fix ci test failed remove whitespace

* print message when no signature help

* Add comment

runtime/lua/vim/lsp/callbacks.lua

@@ -229,16 +229,19 @@ M['textDocument/implementation'] = location_callback
 
 --@see https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_signatureHelp
 M['textDocument/signatureHelp'] = function(_, method, result)
+  -- When use `autocmd CompleteDone <silent><buffer> lua vim.lsp.buf.signature_help()` to call signatureHelp callback
+  -- If the completion item doesn't have signatures It will make noise. Change to use `print` that can use `<silent>` to ignore
+  if not (result and result.signatures and result.signatures[1]) then
+    print('No signature help available')
+    return
+  end
+  local lines = util.convert_signature_help_to_markdown_lines(result)
+  lines = util.trim_empty_lines(lines)
+  if vim.tbl_isempty(lines) then
+    print('No signature help available')
+    return
+  end
   util.focusable_preview(method, function()
-    if not (result and result.signatures and result.signatures[1]) then
-      return { 'No signature available' }
-    end
-    -- TODO show popup when signatures is empty?
-    local lines = util.convert_signature_help_to_markdown_lines(result)
-    lines = util.trim_empty_lines(lines)
-    if vim.tbl_isempty(lines) then
-      return { 'No signature available' }
-    end
     return lines, util.try_trim_markdown_code_blocks(lines)
   end)
 end