Add GetAverageDifficultyForVideo query

src/operations/feed.gql

@@ -50,7 +50,6 @@ fragment VideoCardFields on VideoGQL {
     streamSegmentType
   }
   tableSize
-  pocketSize
   tags {
     tagClasses {
       name

src/operations/video.gql

@@ -211,6 +211,13 @@ query GetMedianRunForVideo($videoId: Int!) {
   }
 }
 
+query GetAverageDifficultyForVideo($videoId: Int!) {
+  getVideo(videoId: $videoId) {
+    id
+    averageDifficulty
+  }
+}
+
 fragment StreamWithEndFrames on UploadStreamGQL {
   id
   streamSegmentType