Update git submodules

* Update docs/submodules/armband from branch 'stable/danube'
  - Update armband documentation for 3.0 release

    Change-Id: I2a71637b67b91cf828bbcf5f6abfbd9c2d6da2eb
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>
    (cherry picked from commit 7dca6641608ea4085cedaf25107c9f702b4cdeb0)

diff --git a/docs/submodules/armband b/docs/submodules/armband
index 1cd256d..2720a12 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit 1cd256dbaf85e4abaf8fb4250e0cb029be43e89a
+Subproject commit 2720a12fea8f0b3296f50a9b0bc8816876586d9d