arrow

ARROW-17715: [CI][C++][Python] Temporary allow failures for s390x on travis (#14138)

The s390x builds currently time out on Travis-CI while compiling Arrow C++.

I'll create a new ticket to follow this up but on the meantime we probably should allow them to fail.

Authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>