Bump mavenVersion from 3.6.3 to 3.9.9

Bumps `mavenVersion` from 3.6.3 to 3.9.9.

Updates `org.apache.maven:maven-artifact` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

Updates `org.apache.maven:maven-core` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

Updates `org.apache.maven:maven-model` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

Updates `org.apache.maven:maven-plugin-api` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

Updates `org.apache.maven:maven-settings` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

Updates `org.apache.maven:maven-compat` from 3.6.3 to 3.9.9
- [Release notes](https://github.com/apache/maven/releases)
- [Commits](apache/maven@maven-3.6.3...maven-3.9.9)

---
updated-dependencies:
- dependency-name: org.apache.maven:maven-artifact
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.maven:maven-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.maven:maven-model
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.maven:maven-plugin-api
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.maven:maven-settings
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.maven:maven-compat
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

pom.xml

@@ -115,7 +115,7 @@ under the License.
 
   <properties>
     <javaVersion>8</javaVersion>
-    <mavenVersion>3.6.3</mavenVersion>
+    <mavenVersion>3.9.9</mavenVersion>
     <resolverVersion>1.4.1</resolverVersion>
     <doxiaVersion>2.0.0-M12</doxiaVersion>
     <doxiaSitetoolsVersion>2.0.0-M19</doxiaSitetoolsVersion>