Update git submodules

Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Euphrates Docs update w odl scenario name cleanups"
  - Euphrates Docs update w odl scenario name cleanups

    - updating docs to reference Euphrates
    - removing the odl_l2-nofeature scenario, it's obsolete
    - renameing odl_l3 to odl, it's default for odl now
    - adding symlinks to files to _l3 files so CI doesn't break
      will remote those once CI is updated to use new names

    Change-Id: I9f2646fc5dac443042c5f4be8cca7d2df5dca663
    Signed-off-by: Dan Radez <dradez@redhat.com>