fix: Adapt to changes in PDL to avoid exception computing date time scales

[pablrod]

Date time scales in some cases were failing with recent version of PDL (at least with version 2.080). Some tests were also failing:

# Failed test 'pretty_breaks'
# at t/06-util_scales.t line 317.
# Caught exception in subtest: Can't locate object method "dt_unpdl" via package "PDL__WITH__PDL::Role::HasNames" at /home/liveapp/.cpanm/work/1659685258.2174913/Chart-GGPlot-0.002000/blib/lib/Chart/GGPlot/Util/Scales.pm line 604.

(fail extracted from cpantesters)

I've tracked the problem to the method PDL::glue not preserving the type anymore.

[iynehz]

Thanks!