[MPMD-302] - Upgrade to PMD 6.22.0

Currently produced (dev) version is 3.13.1-SNAPSHOT,
but the next open release is 3.14.0:
  https://issues.apache.org/jira/projects/MPMD/versions/12346940
diff --git a/pom.xml b/pom.xml
index c9a3627..24b0b97 100644
--- a/pom.xml
+++ b/pom.xml
@@ -89,7 +89,7 @@
     <doxiaVersion>1.9.1</doxiaVersion>
     <doxiaSitetoolsVersion>1.9.2</doxiaSitetoolsVersion>
     <javaVersion>7</javaVersion><!-- Because PMD 5.4+ requires Java 7 -->
-    <pmdVersion>6.21.0</pmdVersion>
+    <pmdVersion>6.22.0</pmdVersion>
     <sitePluginVersion>3.7.1</sitePluginVersion>
     <projectInfoReportsPluginVersion>3.0.0</projectInfoReportsPluginVersion>
     <project.build.outputTimestamp>2020-04-07T21:04:00Z</project.build.outputTimestamp>
diff --git a/src/site/apt/examples/upgrading-PMD-at-runtime.apt.vm b/src/site/apt/examples/upgrading-PMD-at-runtime.apt.vm
index f279dda..1251a52 100644
--- a/src/site/apt/examples/upgrading-PMD-at-runtime.apt.vm
+++ b/src/site/apt/examples/upgrading-PMD-at-runtime.apt.vm
@@ -88,6 +88,8 @@
 *--------------------------------------------------------------------------------*--------------------------------------------------*
 | <<maven-pmd-plugin>>                                                           | <<PMD>>                                          |
 *--------------------------------------------------------------------------------*--------------------------------------------------*
+| {{{https://maven.apache.org/plugins-archives/maven-pmd-plugin-3.14.0/}3.14.0}} | {{{https://pmd.github.io/pmd-6.22.0/}6.22.0}}    |
+*--------------------------------------------------------------------------------*--------------------------------------------------*
 | {{{https://maven.apache.org/plugins-archives/maven-pmd-plugin-3.13.0/}3.13.0}} | {{{https://pmd.github.io/pmd-6.21.0/}6.21.0}}    |
 *--------------------------------------------------------------------------------*--------------------------------------------------*
 | {{{https://maven.apache.org/plugins-archives/maven-pmd-plugin-3.12.0/}3.12.0}} | {{{https://pmd.github.io/pmd-6.13.0/}6.13.0}}    |