Bump gradle-maven-publish-plugin from 0.18.0 to 0.20.0

Bumps [gradle-maven-publish-plugin](https://github.com/vanniktech/gradle-maven-publish-plugin) from 0.18.0 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@0.18.0...0.20.0)

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

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Author: dependabot[bot]

build.gradle

@@ -12,7 +12,7 @@ buildscript {
     }
     dependencies {
         classpath "biz.aQute.bnd:biz.aQute.bnd.gradle:6.0.0"
-        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.18.0'
+        classpath 'com.vanniktech:gradle-maven-publish-plugin:0.20.0'
         classpath "gradle.plugin.com.hierynomus.gradle.plugins:license-gradle-plugin:0.16.1"
     }
 }