fix: Show the Postpone success notice for a bit longer

It's not always readable at all on my mobile devices, by the time
the results have been redrawn.

src/QueryRenderer.ts

@@ -509,6 +509,6 @@ class QueryRenderChild extends MarkdownRenderChild {
         button.disabled = true;
 
         const successMessage = postponementSuccessMessage(postponedDate, updatedDateType);
-        new Notice(successMessage, 1000);
+        new Notice(successMessage, 2000);
     }
 }