Bump com.squareup.okio:okio from 3.17.0 to 3.18.1 - #106

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: whelk-io/maven-settings-xml-action@v22. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/