docs: remove duplicate QuantityFormatter migration sample (#9270)

Author: hl662

docs/quantity-formatting/usage/QuantityFormatterAdvanced.md

@@ -206,17 +206,7 @@ Each of these events covers a different reload trigger, but they all mean the sa
 
 Replace all subscriptions with [QuantityFormatter.onBeforeFormattingReady]($frontend). Register your async loading work via the [FormattingReadyCollector]($quantity) — the formatter awaits all pending work before emitting [QuantityFormatter.onFormattingReady]($frontend).
 
-```ts
-// ✅ Provider work is awaited before formatting is considered ready
-const removeListener = IModelApp.quantityFormatter.onBeforeFormattingReady.addListener((collector) => {
-  collector.addPendingWork(
-    IModelApp.quantityFormatter.addFormattingSpecsToRegistry("MyDomain.PRESSURE", "Units.PA")
-  );
-});
-
-// Single unsubscribe on teardown
-removeListener();
-```
+See the earlier examples in this guide, especially **"Example: Domain spec provider that re-registers on reload"**, for the full provider lifecycle pattern.
 
 **Option B — For tool developers and UI components** (recommended):