(trivial) ci: FTBS: workaround for broken submodule links in libxcb* repos

Several of the libxcb* repos have broken submodule URLs, so the debian image build job breaks while trying to clone them. That's breaking the whole CI pipeline.

Adding a little workaround that's fixing up the broken links, until those repos all have been fixed. Once they're fixed, this commit can be reverted.

Signed-off-by: Enrico Weigelt, metux IT consult info@metux.net