remove delay after dismissing qr-scan-viewcontroller

UIKit seems to be pretty slow in updating underlaying view sometimes,
a quick search for "viewcontroller dismiss completion delayed"
shows several issues.

we ignore this issue by not waiting until the controller is really dismissed,
afaik, ther is no need to do so.

deltachat-ios/Controller/WelcomeViewController.swift

@@ -179,9 +179,8 @@ extension WelcomeViewController: QrCodeReaderDelegate {
             style: .default,
             handler: { [unowned self] _ in
                 self.activateSpinner(true)
-                self.qrCodeReaderNav.dismiss(animated: false) {
-                    self.createAccountFromQRCode()
-                }
+                self.qrCodeReaderNav.dismiss(animated: false)
+                self.createAccountFromQRCode()
             }
         )