Update git submodules

* Update docs/submodules/sdc.git from branch 'master'
  to c9c7f88f77c9cab341485c27e1e67f6294a0b1c2
  - Work around potential NullPointerExceptions in `ToscaOperationFacade`

    - Add tests in `getToscaElementByOperation` and `updateToscaElement` for null values
    - rewrite `getLatestCertifiedByToscaResourceName` in a more functional way
    - Rewrite some other usages of Either in a more functional way

    Issue-ID: SDC-2922
    Signed-off-by: Chris Andre <chris.andre@yoppworks.com>
    Change-Id: I52b294ec91faf9e1054af572dcca4060e62fe571

diff --git a/docs/submodules/sdc.git b/docs/submodules/sdc.git
index 5facedd..c9c7f88 160000 (submodule)
--- a/docs/submodules/sdc.git
+++ b/docs/submodules/sdc.git
@@ -1 +1 @@
-Subproject commit 5facedd4291181fb2668ea3e945687c04fe62cb1
+Subproject commit c9c7f88f77c9cab341485c27e1e67f6294a0b1c2