Update git submodules

* Update docs/submodules/so.git from branch 'master'
  to 21f70778390a1aa248acb97c1c9576419b642dc2
  - Merge "Update css file name in conf.py"
  - Update css file name in conf.py
    
    ribbon.css is the correct name of the css file.
    
    Issue-ID: CIMAN-376
    Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
    Change-Id: I229867d911d28d94f51869c681e98a20f3379465
    
diff --git a/docs/submodules/so.git b/docs/submodules/so.git
index 48aad3a..21f7077 160000
--- a/docs/submodules/so.git
+++ b/docs/submodules/so.git
@@ -1 +1 @@
-Subproject commit 48aad3a3181c6990abb84206027555d473cf71b3
+Subproject commit 21f70778390a1aa248acb97c1c9576419b642dc2