Stop passing Sonatype credentials to reusable workflows

[timtebeek]

• Maven Central publishing was removed in Retire Maven Central publishing and publish snapshots to CGP rewrite-build-gradle-plugin#235, and Stop invoking closeAndReleaseSonatypeStagingRepository and forwarding Sonatype credentials gh-automation#118 stops using the Sonatype credentials. This drops sonatype_username and sonatype_token from the secrets that ci.yml and publish.yml pass to the reusable workflows. Both workflows still declare these secrets as optional, so this is safe to merge before or after gh-automation#118, and it removes one of the callers that must stop passing them before the declarations can go.