docs: clear the pending release notes for 1.6
docs: clear the pending release notes for 1.6

The pending release notes were for v1.5, now cleared for adding
v1.6 features.

Signed-off-by: Travis Nielsen <a8b474fdb3f77f44446f0ab9ddca8147b09b3a9e@redhat.com>

rook/nfs,rook/rook,rook/rook,rook/nfs,rook/rook,rook/rook,rook/rook,rook/nfs