Bump maven-site-plugin from 3.8.2 to 3.9.0 (#3328)

Bumps [maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.8.2 to 3.9.0.
- [Release notes](https://github.com/apache/maven-site-plugin/releases)
- [Commits](https://github.com/apache/maven-site-plugin/compare/maven-site-plugin-3.8.2...maven-site-plugin-3.9.0)
Signed-off-by: Ndependabot-preview[bot] <support@dependabot.com>
Co-authored-by: Ndependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: NMarcello Teodori <151025+mteodori@users.noreply.github.com>

pom.xml

@@ -218,7 +218,7 @@
     <maven-project-info-reports-plugin.version>3.1.0</maven-project-info-reports-plugin.version>
     <maven-release-plugin.version>2.5.3</maven-release-plugin.version>
     <maven-resources-plugin.version>3.1.0</maven-resources-plugin.version>
-    <maven-site-plugin.version>3.8.2</maven-site-plugin.version>
+    <maven-site-plugin.version>3.9.0</maven-site-plugin.version>
     <maven-source-plugin.version>3.2.1</maven-source-plugin.version>
     <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
     <spring-boot.version>2.3.1.RELEASE</spring-boot.version>