qa/suites/rados: temporarily disable ceph-post-file test

qa/suites/rados: temporarily disable ceph-post-file test

Since the lab migration, drop.ceph.com has been unreachable.
This test in the rados suite tries to reach drop.ceph.com and fails
when it can't. We discussed a plan for improving/fixing ceph-post-file
as an nginx server (see details in https://tracker.ceph.com/issues/75995).

This fix will not be immediate though, so for now, I am proposing that we
disable this test until the improved version is available.

I did not remove the following related files in case we end up repurposing them
for the new version:
- https://github.com/ceph/ceph/blob/main/qa/workunits/post-file.sh
- https://github.com/ceph/ceph/blob/main/src/ceph-post-file.in
- https://github.com/ceph/ceph/blob/main/doc/man/8/ceph-post-file.rst

We should re-instate a version of this test in https://tracker.ceph.com/issues/75995.

Fixes: https://tracker.ceph.com/issues/74517
Signed-off-by: Laura Flores <lflores@ibm.com>