[max] Update max version to 25.2

[forfudan]

This pull request includes changes to the mojoproject.toml file, focusing on updating project metadata and dependencies.

Project metadata updates:

• Updated the project description to "A comprehensive decimal and integer mathematics library for Mojo" from "A fixed-point decimal arithmetic library written in Mojo 🔥".
• Commented out the nightly channel URL in the channels list, simplifying the active channels to "https://conda.modular.com/max", "https://repo.prefix.dev/modular-community", and "conda-forge".

Dependency updates:

• Modified the version constraint for the max dependency to ">=25.2" from ">=25.2,<25.3".