Add nproc argument to Coherence.signif_test - #708

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v3, conda-incubator/setup-miniconda@v2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

WARNING conda.cli.condarc:set_key(521): Key auto_activate_base is an alias of auto_activate; setting value with latter