fix: Not populating extension when selecting notebook kernel (microsoft#197619) (microsoft#197810)

When selecting a notebook kernel, prompt was saying
"Select kernel from undefined". "Undefined" here was supported
to be the extension name. When the quick pick items
are generated, they are generated with a value of "label".
Nothing else references or populates a property of "source",
so seems safe to change the code to reference "label" instead.

Author: tomqwpl

src/vs/workbench/contrib/notebook/browser/viewParts/notebookKernelQuickPickStrategy.ts

@@ -600,7 +600,7 @@ export class KernelPickerMRUStrategy extends KernelPickerStrategyBase {
 				await this._selecteKernel(notebook, selectedKernelPickItem.kernel);
 				return true;
 			} else if (isGroupedKernelsPick(selectedKernelPickItem)) {
-				await this._selectOneKernel(notebook, selectedKernelPickItem.source, selectedKernelPickItem.kernels);
+				await this._selectOneKernel(notebook, selectedKernelPickItem.label, selectedKernelPickItem.kernels);
 				return true;
 			} else if (isSourcePick(selectedKernelPickItem)) {
 				// selected explicilty, it should trigger the execution?