[CQ] remove deprecated Disposer.isDisposed invocation (#8377)

Removes deprecated `Disposer.isDisposed` invocation. (Invoking method is
unused.)

Verifier output:

```
     #Deprecated method com.intellij.openapi.util.Disposer.isDisposed(Disposable) invocation
          Deprecated method com.intellij.openapi.util.Disposer.isDisposed(com.intellij.openapi.Disposable disposable) : boolean is invoked in io.flutter.vmService.VMServiceManager.hasServiceExtension(String, Consumer, Disposable) : void
```

---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide]([https://github.com/dart-lang/sdk/blob/main/CONTRIBUTING.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview)
for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Dart contributions to our repos should follow the [Dart style
guide](https://dart.dev/guides/language/effective-dart) and use `dart
format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin
best practices
([discussion](#8098)).
</details>

Author: pq

src/io/flutter/vmService/VMServiceManager.java

@@ -9,7 +9,6 @@
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.intellij.openapi.Disposable;
-import com.intellij.openapi.util.Disposer;
 import com.intellij.openapi.util.text.StringUtil;
 import io.flutter.run.daemon.FlutterApp;
 import io.flutter.utils.EventStream;
@@ -415,12 +414,6 @@ public boolean hasServiceExtensionNow(String name) {
     }
   }
 
-  public void hasServiceExtension(String name, Consumer<Boolean> onData, Disposable parentDisposable) {
-    if (!Disposer.isDisposed(parentDisposable)) {
-      Disposer.register(parentDisposable, hasServiceExtension(name, onData));
-    }
-  }
-
   public boolean hasRegisteredService(String name) {
     return registeredServices.contains(name);
   }