Don't throw error if user cancels out of choosing a language (#2365)

When running "Create Query", if the user escapes out of the language quickpick we don't need to throw an error. Instead we can just show a `UserCancellationException` notice.

extensions/ql-vscode/src/skeleton-query-wizard.ts

@@ -141,7 +141,7 @@ export class SkeletonQueryWizard {
       maxStep: 3,
     });
 
-    return await askForLanguage(this.cliServer, false);
+    return await askForLanguage(this.cliServer, true);
   }
 
   private async createQlPack() {