Bump maven-plugin-api from 3.8.3 to 3.8.4 (GoogleContainerTools#3508)

Bumps [maven-plugin-api](https://github.com/apache/maven) from 3.8.3 to 3.8.4.
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.8.3...maven-3.8.4)

---
updated-dependencies:
- dependency-name: org.apache.maven:maven-plugin-api
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle

@@ -36,7 +36,7 @@ project.ext.dependencyStrings = [
   ASM: 'org.ow2.asm:asm:9.2',
   PICOCLI: 'info.picocli:picocli:4.6.2',
 
-  MAVEN_API: 'org.apache.maven:maven-plugin-api:3.8.3',
+  MAVEN_API: 'org.apache.maven:maven-plugin-api:3.8.4',
   MAVEN_CORE: 'org.apache.maven:maven-core:3.8.4',
   MAVEN_COMPAT: 'org.apache.maven:maven-compat:3.8.3',
   MAVEN_PLUGIN_ANNOTATIONS: 'org.apache.maven.plugin-tools:maven-plugin-annotations:3.6.1',