Default Nodejs Version has deprecation warning

[Akatuoro]

Currently Node.js 18 is the default.
During staging, this results in the warning:

   **WARNING** node 18.x.x will no longer be available in new buildpacks released after 2025-04-30.

The active Node.js version is 22.

[robdimsdale]

I think you can probably PR the requisite changes in to the manifest file. I think the automation will respect these changes, but if not, we'll find out after the changes are made.

[ivanovac]

Node.js Buildpack v1.8.40 is released and it does not contains node v18 anymore.