Bump com.netflix.nebula:nebula-publishing-plugin in /buildSrc

Bumps [com.netflix.nebula:nebula-publishing-plugin](https://github.com/nebula-plugins/nebula-publishing-plugin) from 20.3.0 to 21.0.0.
- [Release notes](https://github.com/nebula-plugins/nebula-publishing-plugin/releases)
- [Changelog](https://github.com/nebula-plugins/nebula-publishing-plugin/blob/main/CHANGELOG.md)
- [Commits](nebula-plugins/nebula-publishing-plugin@v20.3.0...v21.0.0)

---
updated-dependencies:
- dependency-name: com.netflix.nebula:nebula-publishing-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

buildSrc/build.gradle

@@ -106,7 +106,7 @@ dependencies {
   api 'org.apache.commons:commons-compress:1.24.0'
   api 'org.apache.ant:ant:1.10.14'
   api 'com.netflix.nebula:gradle-extra-configurations-plugin:10.0.0'
-  api 'com.netflix.nebula:nebula-publishing-plugin:20.3.0'
+  api 'com.netflix.nebula:nebula-publishing-plugin:21.0.0'
   api 'com.netflix.nebula:gradle-info-plugin:12.1.6'
   api 'org.apache.rat:apache-rat:0.15'
   api 'commons-io:commons-io:2.13.0'