Update PhotoViewModel to java 8 syntax

Updating leanback's PhotoViewModel class to
utilize java 8 lamba syntax.

Test: ./gradlew bOS
Bug: 240298691
Change-Id: I5d9c7fb056291c2cbffdf936d1b87cc252aab97f
diff --git a/samples/SupportLeanbackDemos/src/main/java/com/example/android/leanback/PhotoViewModel.java b/samples/SupportLeanbackDemos/src/main/java/com/example/android/leanback/PhotoViewModel.java
index 9fe6a2b..9b446f2 100644
--- a/samples/SupportLeanbackDemos/src/main/java/com/example/android/leanback/PhotoViewModel.java
+++ b/samples/SupportLeanbackDemos/src/main/java/com/example/android/leanback/PhotoViewModel.java
@@ -17,7 +17,6 @@
 
 import android.app.Application;
 
-import androidx.arch.core.util.Function;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Transformations;
@@ -51,14 +50,12 @@
         );
 
         mPagingDataLiveData = Transformations.map(PagingLiveData.getLiveData(pager),
-                (Function<PagingData<Photo>, PagingData<PhotoItem>>) pagingData ->
+                pagingData ->
                         PagingDataTransforms.map(pagingData, mExecutor,
                                 (photo) -> new PhotoItem(photo.getTitle(),
                                         photo.getImgResourceId(),
                                         photo.getId()))
         );
-
-
     }
 
     public LiveData<PagingData<PhotoItem>> getPagingDataLiveData() {