Make friends filter button more visible

This commit changes the appearance of the friends filter button to make it more visible

Testing:
- Checked appearance in both light mode and dark mode
- Checked appearance in all usages (notifications view and DM view)
- Checked consistency against the filter button in Universe view

Changelog-Changed: Improve visibility of friends filter button
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>

damus/Views/Buttons/FriendsButton.swift

@@ -28,7 +28,7 @@ struct FriendsButton: View {
                 Image("user-added")
                     .resizable()
                     .frame(width: 28, height: 28)
-                    .foregroundColor(DamusColors.adaptableGrey)
+                    .foregroundColor(.gray)
             }
         }
         .buttonStyle(.plain)