Bump maven-site-plugin from 3.7 to 3.9.1

Bumps [maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.7 to 3.9.1.
- [Release notes](https://github.com/apache/maven-site-plugin/releases)
- [Commits](https://github.com/apache/maven-site-plugin/compare/maven-site-plugin-3.7...maven-site-plugin-3.9.1)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-site-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/pom.xml b/pom.xml
index 7e5f88a..5cd0438 100644
--- a/pom.xml
+++ b/pom.xml
@@ -192,7 +192,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-site-plugin</artifactId>
-        <version>3.7</version>
+        <version>3.9.1</version>
         <configuration>
           <outputEncoding>${project.build.sourceEncoding}</outputEncoding>
           <inputEncoding>${project.build.sourceEncoding}</inputEncoding>