Enable whitespace rendering on selection in Monaco (go-gitea#24444)

Remove the
[renderWhitespace](https://microsoft.github.io/monaco-editor/docs.html#interfaces/editor.IEditorOptions.html#renderWhitespace)
override, so the default value of `selection` takes over and makes
whitespace visible on selection.

<img width="128" alt="Screenshot 2023-04-30 at 19 09 41"
src="https://user-images.githubusercontent.com/115237/235366707-d598268d-03cc-4839-a195-c460bddae99b.png">

Co-authored-by: Giteabot <[email protected]>

Author: silverwind

web_src/js/features/codeeditor.js

@@ -14,7 +14,6 @@ const baseOptions = {
   overviewRulerLanes: 0,
   renderLineHighlight: 'all',
   renderLineHighlightOnlyWhenFocus: true,
-  renderWhitespace: 'none',
   rulers: false,
   scrollbar: {horizontalScrollbarSize: 6, verticalScrollbarSize: 6},
   scrollBeyondLastLine: false,