Switched back to version `3.9.1` of `maven-site-plugin`

* Version `3.21.0` did not build the Java-API-documentation and several
  other pages with the given configuration.
* It should also be possible, to fix the configuration. But switching back
  to the older version of the plugin was the quicker workaround.

diff --git a/pom.xml b/pom.xml
index 4e5b45b5efc49c9c6bb1a6ebc3e937bcc356cfed..00bd9ddc0b4b3f82b657134124197f7928cfafd3 100644 (file)
--- a/pom.xml
+++ b/pom.xml
@@ -344,7 +344,7 @@
       </plugin>
       <plugin>
         <artifactId>maven-site-plugin</artifactId>
-        <version>3.21.0</version>
+        <version>3.9.1</version>
         <configuration>
           <siteDirectory>${project.build.directory}/filtered-site</siteDirectory>
         </configuration>