Update asset for "add more images to album" button.

Signal/Images.xcassets/album_add_more.imageset/Contents.json

@@ -2,17 +2,17 @@
   "images" : [
     {
       "idiom" : "universal",
-      "filename" : "add-photo-24@1x.png",
+      "filename" : "create-album-outline-32@1x.png",
       "scale" : "1x"
     },
     {
       "idiom" : "universal",
-      "filename" : "add-photo-24@2x.png",
+      "filename" : "create-album-outline-32@2x.png",
       "scale" : "2x"
     },
     {
       "idiom" : "universal",
-      "filename" : "add-photo-24@3x.png",
+      "filename" : "create-album-outline-32@3x.png",
       "scale" : "3x"
     }
   ],