Adopt nebula.release plugin v19 after failure to resolve grgit

[timtebeek]

What's changed?

Move from v16 and different groupId to v19

• https://plugins.gradle.org/plugin/nebula.release
• https://github.com/nebula-plugins/nebula-release-plugin/releases/tag/v17.0.0
• https://github.com/nebula-plugins/nebula-release-plugin/releases/tag/v18.0.0
• https://github.com/nebula-plugins/nebula-release-plugin/releases/tag/v19.0.0

What's your motivation?

    > Caused by: org.gradle.internal.resolve.ModuleVersionNotFoundException: Could not find org.ajoberstar.grgit:grgit-core:4.0.2.
    > Searched in the following locations:
    >   - file:/home/tim/.m2/repository/org/ajoberstar/grgit/grgit-core/4.0.2/grgit-core-4.0.2.pom
    >   - https://repo.maven.apache.org/maven2/org/ajoberstar/grgit/grgit-core/4.0.2/grgit-core-4.0.2.pom
    >   - https://plugins.gradle.org/m2/org/ajoberstar/grgit/grgit-core/4.0.2/grgit-core-4.0.2.pom
    > Required by:
    >     project : > project :build-src > com.netflix.nebula:nebula-release-plugin:16.0.0
    > 
    > 
    > BUILD FAILED in 12s

[timtebeek]

Had noticed this one failed to build & ingest; possibly since the Gradle plugin portal switched from JCenter to Maven Central.

There's a few more spots where we could potentially standardize these plugin ids & versions:
https://github.com/search?q=org%3Aopenrewrite%20%22nebula.release%22&type=code