Update git submodules

* Update requirements from branch 'master'
  to 13f27bd15c478df868af6c67f67b1c4f3e782745
  - Downgrade pillow to 9.5.0
    
    The latest blockdiag is not compatible with pillow 10.y.z[1].
    
    The library looks unmaintained, so we may have to consider replacing
    it, but let's downgrade pillow to fix broken nova doc builds.
    
    [1] blockdiag/blockdiag#178
    
    Change-Id: I58f0c06f122fd3b5ad349d1bdd25d5417dc0e39d