node24 support

Node v20 is going to be EOL in April 2026 -- https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

The current release runs using node20 -- https://github.com/webfactory/ssh-agent/blob/v0.9.1/action.yml#L23

For past reference node18 -> node20 was done via https://github.com/webfactory/ssh-agent/pull/201