prefer UIImage(named:) over #imageLiteral

`#imageLiteral` make it hard in xcode to see what is going on
(they are replaced by some icon, so you cannot easily see the name of the image),
also, searching a bit, it seems, `UIImage(named:)` is quite the same -
but with less weird xcode issue we did not encounter yet :)

deltachat-ios/Controller/AccountSwitchViewController.swift

@@ -271,7 +271,7 @@ class AccountCell: UITableViewCell {
         view.translatesAutoresizingMaskIntoConstraints = false
         view.widthAnchor.constraint(equalToConstant: 16).isActive = true
         view.tintColor = DcColors.middleGray
-        view.image = #imageLiteral(resourceName: "volume_off").withRenderingMode(.alwaysTemplate)
+        view.image = UIImage(named: "volume_off")?.withRenderingMode(.alwaysTemplate)
         view.contentMode = .scaleAspectFit
         view.isAccessibilityElement = false
         return view