Update git submodules
Update git submodules

* Update plugins/plugin-manager from branch 'master'
  to 783f5c65c7dca522658efe10d57d1ac9ab5f9007
  - Add Gerrit logo to the intro page
    
    After 12 years of the Gerrit Code Review project
    add the logo to the splash page [1] displayed in the
    out of the box experience of Gerrit.
    
    By showing the diffy logo on the very first page
    the new users see when they first run Gerrit, the
    product gives the message of a renewed attention
    to the design and user-experience of modern
    Gerrit v3.
    
    [1] https://imgur.com/5gpumX8
    
    Change-Id: I6e7085759153c584350ce41e56328298f4f1954c
    
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