Update ipa/login-screen-background.jpg
    
    - Change the source file ipa/login-screen-background.jpg from blue to
      graycale to make it consistent with application ui interface, wish is
      also in that grayscale tone. This makes the transition from login
      screen to main ui screen nicer. The file was also resized from 1200x670
      to 1200x690 pixels to preserve image proportions.
    
      Artwork example is at https://wiki.centos.org/ArtWork/Motifs/CentOS8/Sketch4?action=show#head-64eb25344b8400edc01c542a1677bfee94da18df