Fixes #127439: changes keys to a function

src/vs/vscode.d.ts

@@ -6215,9 +6215,11 @@ declare module 'vscode' {
 	export interface Memento {
 
 		/**
-		 * The stored keys.
+		 * Returns the stored keys.
+		 *
+		 * @return The stored keys.
 		 */
-		readonly keys: readonly string[];
+		keys(): readonly string[];
 
 		/**
 		 * Return a value.

src/vs/workbench/api/common/extHostMemento.ts

@@ -56,7 +56,7 @@ export class ExtensionMemento implements vscode.Memento {
 		}, 0);
 	}
 
-	get keys(): readonly string[] {
+	keys(): readonly string[] {
 		// Filter out `undefined` values, as they can stick around in the `_value` until the `onDidChangeStorage` event runs
 		return Object.entries(this._value ?? {}).filter(([, value]) => value !== undefined).map(([key]) => key);
 	}