ci-dockerslaves-cleanup: Remove x86-64-TF-06 again

As somehow running this job leads to host's subbuild hanging with:
(pending—There are no nodes with the label ‘x86-64-TF-06’), even though
that cloud clearly exists and runs the actual CI builds.

https://linaro.atlassian.net/browse/STG-5588

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I54aab94e495ecfebe5c6f9e41ec45b8df41c6f4e
1 file changed