[video_player]: Bump robolectric from 4.4 to 4.8.1 in /packages/video_player/video_player/example/android/app (flutter#6025)

Author: dependabot[bot]

packages/video_player/video_player/example/android/app/build.gradle

@@ -59,7 +59,7 @@ flutter {
 
 dependencies {
     testImplementation 'junit:junit:4.13'
-    testImplementation 'org.robolectric:robolectric:4.4'
+    testImplementation 'org.robolectric:robolectric:4.8.1'
     testImplementation 'org.mockito:mockito-core:3.5.13'
     androidTestImplementation 'androidx.test:runner:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'