Unpin conda-build

[jakirkham]

When making updates previously, conda-build 25.3 was released: conda/conda-build#5632

This introduced some issues with the XGBoost builds: #224 (comment)

...
Here is one such error from CI:

conda_libmamba_solver.conda_build_exceptions.ExplainedDependencyNeedsBuildingError: Unsatisfiable dependencies for platform osx-64: {MatchSpec("numpy[version='1.26,==2.0.2.*',build=py39h277832c_1]")}
Encountered problems while solving:
  - unsupported request

Could not solve for environment specs
The following package could not be installed
└─ numpy =1.26,==2.0.2 py39h277832c_1 does not exist (perhaps a typo or a missing channel).

...

To workaround the issues, we simply pinned conda-build to the last known working version 25.1

xgboost-feedstock/conda-forge.yml

Lines 17 to 19 in d8e38c9

	remote_ci_setup:
	- conda-forge-ci-setup=4
	- conda-build=25.1

Since then the problematic conda-build 25.3 build was marked broken: conda-forge/admin-requests#1450

The underlying issue was fixed: conda/conda-build#5644

Also conda-build version 25.3.1 was released: conda/conda-build#5652

So it should be possible to relax this conda-build pin

[jakirkham]

It is worth noting that conda-build version 25.4.0 was released yesterday: conda-forge/admin-requests#1496

Then was promptly marked broken: conda-forge/admin-requests#1496

This was due to a different upstream issue ( conda/conda-build#5689 ), which appears fixed, but not released

May let conda-build 25.4.x simmer before trying to unpin

[jakirkham]

Alternatively it could be worth just trying using a newer pin to get 25.3 and see how that goes for us