Bump gradle-maven-publish-plugin from 0.19.0 to 0.20.0

Bumps [gradle-maven-publish-plugin](https://github.com/vanniktech/gradle-maven-publish-plugin) from 0.19.0 to 0.20.0.
- [Release notes](https://github.com/vanniktech/gradle-maven-publish-plugin/releases)
- [Changelog](https://github.com/vanniktech/gradle-maven-publish-plugin/blob/master/CHANGELOG.md)
- [Commits](vanniktech/gradle-maven-publish-plugin@0.19.0...0.20.0)

---
updated-dependencies:
- dependency-name: com.vanniktech:gradle-maven-publish-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle

@@ -16,7 +16,7 @@ buildscript {
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
 
-        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.19.0'
+        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.20.0'
     }
 }