Update caption indicator asset.

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

@@ -2,17 +2,17 @@
   "images" : [
     {
       "idiom" : "universal",
-      "filename" : "caption-24@1x.png",
+      "filename" : "caption-shadow-24@1x.png",
       "scale" : "1x"
     },
     {
       "idiom" : "universal",
-      "filename" : "caption-24@2x.png",
+      "filename" : "caption-shadow-24@2x.png",
       "scale" : "2x"
     },
     {
       "idiom" : "universal",
-      "filename" : "caption-24@3x.png",
+      "filename" : "caption-shadow-24@3x.png",
       "scale" : "3x"
     }
   ],

Signal/src/ViewControllers/ConversationView/Cells/MediaAlbumCellView.swift

@@ -171,8 +171,7 @@ public class MediaAlbumCellView: UIStackView {
                 owsFailDebug("Couldn't load icon.")
                 continue
             }
-            let iconView = UIImageView(image: icon.withRenderingMode(.alwaysTemplate))
-            iconView.tintColor = .ows_white
+            let iconView = UIImageView(image: icon)
             itemView.addSubview(iconView)
             itemView.layoutMargins = .zero
             iconView.autoPinTopToSuperviewMargin(withInset: 6)