Update git submodules

* Update docs/submodules/portal.git from branch 'master'
  to 751a5e5776b4615c8d3333f7b7d37d17bbf775ba
  - Merge "Migrate portal docs"
  - Migrate portal docs

    Merging this will create
    https://onap-portal.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: I9635190029f31bd06068b30f26e63af73738a342

diff --git a/docs/submodules/portal.git b/docs/submodules/portal.git
index 6e50276..751a5e5 160000 (submodule)
--- a/docs/submodules/portal.git
+++ b/docs/submodules/portal.git
@@ -1 +1 @@
-Subproject commit 6e50276a42ab82cfe34ced9cf97e545283f37f2a
+Subproject commit 751a5e5776b4615c8d3333f7b7d37d17bbf775ba