Fix conda activate for conda>=25.11

[Zaubentrucker]

From conda version 25.11, the conda info --envs --json command no longer contains the env_dirs field, as described in conda/conda#15353.

This would cause the conda activate <env-name> command in this script to always fail.:

~> conda activate test
Error: nu::shell::name_not_found

  × Name not found
    ╭─[C:\Users\zaubentrucker\AppData\Roaming\nushell\scripts\conda.nu:98:21]
 97 │     let env_dirs = (
 98 │         $conda_info.envs_dirs |
    ·                     ────┬────
    ·                         ╰── did you mean 'envs_details'?
 99 │         each { || path join $env_name }
    ╰────

~>  

The missing info is still contained in conda info --json however, so we can just switch to that.

[fdncred]

Thanks