Update git submodules

* Update docs/submodules/opera from branch 'master'
  - Add known issue in docs

    Change-Id: Ia02802eeeac10a490dac612348adaf2908347021
    Signed-off-by: Harry Huang <huangxiangyu5@huawei.com>

diff --git a/docs/submodules/opera b/docs/submodules/opera
index 59feacf..645898c 160000 (submodule)
--- a/docs/submodules/opera
+++ b/docs/submodules/opera
@@ -1 +1 @@
-Subproject commit 59feacf3bf7a46819b5884bd5ed25b73c5334da7
+Subproject commit 645898cb63b05c96f7fc15aa3934af12d988cd33