Bump doxiaVersion from 2.0.0-M12 to 2.0.0

Bumps `doxiaVersion` from 2.0.0-M12 to 2.0.0.

Updates `org.apache.maven.doxia:doxia-sink-api` from 2.0.0-M12 to 2.0.0
- [Release notes](https://github.com/apache/maven-doxia/releases)
- [Commits](apache/maven-doxia@doxia-2.0.0-M12...doxia-2.0.0)

Updates `org.apache.maven.doxia:doxia-core` from 2.0.0-M12 to 2.0.0
- [Release notes](https://github.com/apache/maven-doxia/releases)
- [Commits](apache/maven-doxia@doxia-2.0.0-M12...doxia-2.0.0)

Updates `org.apache.maven.doxia:doxia-module-apt` from 2.0.0-M12 to 2.0.0

Updates `org.apache.maven.doxia:doxia-module-xdoc` from 2.0.0-M12 to 2.0.0

---
updated-dependencies:
- dependency-name: org.apache.maven.doxia:doxia-sink-api
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.apache.maven.doxia:doxia-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.apache.maven.doxia:doxia-module-apt
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.apache.maven.doxia:doxia-module-xdoc
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -59,7 +59,7 @@
     <javaVersion>8</javaVersion>
     <mavenVersion>3.6.3</mavenVersion>
     <resolverVersion>1.4.1</resolverVersion>
-    <doxiaVersion>2.0.0-M12</doxiaVersion>
+    <doxiaVersion>2.0.0</doxiaVersion>
     <doxiaSitetoolsVersion>2.0.0-M19</doxiaSitetoolsVersion>
     <reportingApiVersion>4.0.0-M12</reportingApiVersion>
     <pluginToolsVersion>3.13.0</pluginToolsVersion>