Import from collections.abc to silence a deprecation warning

[ldaverio]

collections.abc exists in all currently supported python versions (2.7, 3.5+), so the proposed fix shouldn't pose any problem

[ali96343]

cool !
it works with python 3.11
thanks !

[stheid]

I think its time to merge that pr. pyjade becomes more and more broken because the fraction of users stuck at 3.9 gets smaller and smaller