contrib/bc: temporarily disconnect the tests for 5.0.2

The tests that come with version 5.0.2 have been extended to cover the
line editing functions. It has been found that these tests generate
false negative results in FreeBSD, most likely due to an issue in the
pexpect functionality used.

These history tests are skipped on systems that do not have python and
py-pexpect installed (and thus are unlikely to cause CI test failures),
but in order to not cause irritating failures on systems were these
packages are in fact installed, I temporarily disconnect them.

I had planned to skip this version due to the issue with the history
tests, but some committer has asked me to go ahead since the currently
used version 5.0.0 contains a macro name that collides with a project
he is working on.

No MFC of this version is planned. A version 5.0.3 is expected to be
released soon, and that version will allow to reconnect the tests and
will be MFCed.