Update conda recipe to Flit Core 4

[harryswift01]

Summary

This PR updates the conda recipe to use Flit Core 4, keeping the conda build dependency aligned with the project’s updated build-system requirements.

Changes

Conda build dependency:

• Updated flit-core from >=3.4,<4 to >=4,<5 in conda-recipe/meta.yaml.

Impact

• Keeps the conda build environment consistent with the Flit 4 configuration used by the project.
• Prevents the conda recipe from continuing to constrain builds to Flit Core 3.