Temporarily disable installcheck for test_oat_hooks module
Buildfarm members are encountering errors when the test is run under
various locales/encodings. As the buildfarm only does this for
installchecks, disable them for now.
Discussion: https://postgr.es/m/
6067945b-960a-ab04-d40f-
06b006a1dcd0@dunslane.net