Update javadoc for getDeclaredInstances.

Test: Javadoc changes
Bug: 259363062
Change-Id: Ibc99e71abbec01853f0eae187ee0d75f9fe94bfe

core/java/android/os/ServiceManager.java

@@ -252,10 +252,12 @@ public final class ServiceManager {
     }
 
     /**
-     * Returns the list of declared instances for an interface.
+     * Returns an array of all declared instances for a particular interface.
+     *
+     * For instance, if 'android.foo.IFoo/foo' is declared (e.g. in VINTF
+     * manifest), and 'android.foo.IFoo' is passed here, then ["foo"] would be
+     * returned.
      *
-     * @return true if the service is declared somewhere (eg. VINTF manifest) and
-     * waitForService should always be able to return the service.
      * @hide
      */
     @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)