Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to 54b8c6d11a5bb8111b6d991258b77c4a41a500cb
  - replace deprecated JsonSerialize.Inclusion

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
    was deprecated

    use @JsonInclude(Include.NON_NULL) instead
    to suppress when property is NULL

    Issue-ID: APPC-1764
    Change-Id: I1bbe10a156166bc37a167122ff68d1dc183fcd2f
    Signed-off-by: Taka Cho <takamune.cho@att.com>

diff --git a/docs/submodules/appc.git b/docs/submodules/appc.git
index e48727b..54b8c6d 160000 (submodule)
--- a/docs/submodules/appc.git
+++ b/docs/submodules/appc.git
@@ -1 +1 @@
-Subproject commit e48727b615d84e00f681359b899912cdfc65d876
+Subproject commit 54b8c6d11a5bb8111b6d991258b77c4a41a500cb