[submodule] Advance sonic-dbsyncd pointer

fa8b709 Handled the error case of negative age (#57)
990f5b0 Use github code scanning instead of LGTM (#55)
a7992c5 Install libyang for swss-common. (#50)
244fa86 Update README.md

Signed-off-by: Vivek Reddy Karri <vkarri@nvidia.com>