Update opacity on hover on top insert toolbar (#129863)

Author: rebornix

src/vs/workbench/contrib/notebook/browser/media/notebook.css

@@ -730,6 +730,8 @@
 	opacity: 1;
 } */
 
+.monaco-workbench .notebookOverlay .cell-list-top-cell-toolbar-container:focus-within,
+.monaco-workbench .notebookOverlay .cell-list-top-cell-toolbar-container:hover,
 .monaco-workbench .notebookOverlay.notebook-editor-editable > .cell-list-container > .monaco-list > .monaco-scrollable-element > .monaco-list-rows > .monaco-list-row .cell-bottom-toolbar-container:hover,
 .monaco-workbench .notebookOverlay.notebook-editor-editable > .cell-list-container > .monaco-list > .monaco-scrollable-element > .monaco-list-rows > .monaco-list-row .cell-bottom-toolbar-container:focus-within {
 	opacity: 1;