Revert "meson: Fix the reference to libxml2 path"

It seemed to be what the wrap file expected but in the end it is
just a bug in meson which is now fixed.

This reverts commit cc5d74d0.
3 jobs for libxml2_wrap in 8 minutes and 2 seconds (queued for 5 seconds)
Status Name Job ID Coverage
  Preparation
passed manifest #50837

00:00:29

 
  Build
passed build fedora x86_64 #50838

00:03:23

 
  Full Builds
passed build android arm64 api28 #50839

00:04:08