build: update GT4Py (loop layout fixes & horizontal regions syntax cleanup)

[romanc]

Description

This PR updates GT4Py to bring the following two fixes:

• Remove redundant horizontal region syntax
• Fix loop reordering in schedule tree

How has this been tested?

All good as long as CI is still green.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation (e.g. add new modules to docs/docstrings/): N/A
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included: N/A