chore: remove luarocks dependency to lrexlib-pcre
chore: remove luarocks dependency to lrexlib-pcre

This does not remove the installation of pcre in the package build or the
openresty installation of travis-ci.

ejoncas/kong,vzaramel/kong,kyroskoh/kong,streamdataio/kong,salazar/kong,smanolache/kong,rafael/kong,ccyphers/kong,ind9/kong,isdom/kong,icyxp/kong,Vermeille/kong,jerizm/kong,streamdataio/kong,jebenexer/kong,li-wl/kong,shiprabehera/kong,Kong/kong,xvaara/kong,Kong/kong,beauli/kong,Mashape/kong,ajayk/kong,kyroskoh/kong,vzaramel/kong,Kong/kong,akh00/kong,isdom/kong,ind9/kong,ejoncas/kong,rafael/kong