Update git submodules

* Update docs/submodules/modeling/modelspec.git from branch 'master'
  to 51df70ea00e53e93f4fc337b3e9f4bfd28cf7b5d
  - Update enhanced service model

    Main changes are the ServiceProperties part, add 3GPP attributes in a
    new diagram"ServiceProperties", add a new attribute"maxAvailableNumber"
    in ServiceDescriptor, supplement stereotype in the model.

    Issue-ID: MODELING-104

    Change-Id: I6ff4961e4bc21b564b5a17ffa702dbd78ccfb186

    Change-Id: I6ff4961e4bc21b564b5a17ffa702dbd78ccfb186
    Signed-off-by: guochuyicmri <guochuyi@chinamobile.com>

diff --git a/docs/submodules/modeling/modelspec.git b/docs/submodules/modeling/modelspec.git
index 149a9fb..51df70e 160000 (submodule)
--- a/docs/submodules/modeling/modelspec.git
+++ b/docs/submodules/modeling/modelspec.git
@@ -1 +1 @@
-Subproject commit 149a9fb31eab12a86d28f73aaa2ba4a05343e0fe
+Subproject commit 51df70ea00e53e93f4fc337b3e9f4bfd28cf7b5d