Update git submodules

* Update docs/submodules/music.git from branch 'master'
  to 9399b2eed91169c719acd9a966b4c5ed560897a8
  - Migrate music docs

    Merging this will create
    https://onap-music.readthedocs.io
    This build will run in parallel
    to the current docs generation method
    until we are ready to cut over.

    Issue-ID: CIMAN-364
    Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
    Change-Id: Icbac29b0d981370c9e0db7937b2acef97387ed2e

diff --git a/docs/submodules/music.git b/docs/submodules/music.git
index 8ca9a7f..9399b2e 160000 (submodule)
--- a/docs/submodules/music.git
+++ b/docs/submodules/music.git
@@ -1 +1 @@
-Subproject commit 8ca9a7f168a141f15280662d50d6d4c933dde3bc
+Subproject commit 9399b2eed91169c719acd9a966b4c5ed560897a8