Update git submodules

* Update docs/submodules/externalapi/nbi.git from branch 'master'
  to c4b865137354f422efb46f0f6efa846d1353239d
  - Merge "Initial draft of Frankfurt Release notes for RC0"
  - Initial draft of Frankfurt Release notes for RC0
    
    Issue-ID: EXTAPI-409
    
    Signed-off-by: aosull01 <adrian.osullivan@huawei.com>
    Change-Id: Icc190c8f1d5b10902f4676b425babc46807232dd
    
diff --git a/docs/submodules/externalapi/nbi.git b/docs/submodules/externalapi/nbi.git
index 4a0e63d..c4b8651 160000
--- a/docs/submodules/externalapi/nbi.git
+++ b/docs/submodules/externalapi/nbi.git
@@ -1 +1 @@
-Subproject commit 4a0e63de303169e653758943858ec7fa9d52af16
+Subproject commit c4b865137354f422efb46f0f6efa846d1353239d