Remove infra submodule dir, dir was not removed.

Dir must be removed when submodule is de-inited

Change-Id: Ied3aa418394108955fc3217f480fc3f2fdc76da6
Signed-off-by: agardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/infra b/docs/submodules/infra
deleted file mode 160000 (submodule)
index 70abc78..0000000
--- a/docs/submodules/infra
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 70abc782669332240354aad59d03c0fa7a7e2c51