build-unit-test-docker: Bump libvncserver

This commit bumps libvncserver to get the revision which sub-tree
recipe indicates:
meta-openembedded/meta-oe/recipes-graphics/libvncserver

There is no issue in real build because this revision was merged
in LibVNCServer-0.9.12 but this fix is required to resolve CI
build issue in:
https://gerrit.openbmc-project.xyz/c/openbmc/obmc-ikvm/+/21483

Change-Id: I23f3265085f180ffe4fea204e67cfed68678c52b
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
1 file changed