CI: gdxdiff fails on TIMES-NZ

[olejandro]

Somehow gdxdiff consistently fails on TIMES-NZ on the first pass. Re-running the CI solves the issue; e.g. attempt 1 and 2.

[siddharth-krishna]

Hmmm I'm not able to reproduce this locally. I also tried to make a little test PR, and it ran on the first pass in that one too: #267

Let me know if you see this issue again, perhaps?

[olejandro]

It showed up again here: https://github.com/etsap-TIMES/xl2times/actions/runs/12788734823/job/35650627029