Switch 2.x versions to 2021.x release train.

Closes #1591

Author: mp911de

parent/pom.xml

@@ -137,7 +137,7 @@
 		<javax-annotation-api>1.3.2</javax-annotation-api>
 
 		<!-- Used in asciidoc reference documentation -->
-		<releasetrain>2022.0.0-SNAPSHOT</releasetrain>
+		<releasetrain>2021.2.0-SNAPSHOT</releasetrain>
 
 		<!-- To be overridden by individual modules -->
 		<java-module-name/>