[mob][photos] Cleanup face models

mobile/lib/face/model/detection.dart

@@ -46,10 +46,6 @@ class Detection {
     );
   }
 
-  int getFaceArea(int imageWidth, int imageHeight) {
-    return (box.width * imageWidth * box.height * imageHeight).toInt();
-  }
-
   FaceDirection getFaceDirection() {
     if (isEmpty) {
       return FaceDirection.straight;

mobile/lib/face/model/face.dart

@@ -31,13 +31,6 @@ class Face {
 
   bool get isHighQuality => (!isBlurry) && hasHighScore;
 
-  int area({int? w, int? h}) {
-    return detection.getFaceArea(
-      fileInfo?.imageWidth ?? w ?? 0,
-      fileInfo?.imageHeight ?? h ?? 0,
-    );
-  }
-
   Face(
     this.faceID,
     this.fileID,