set version to 1.2.1-SNAPSHOT

Signed-off-by: Peter Gafert <peter.gafert@archunit.org>

Author: codecholeric

gradle.properties

@@ -1,4 +1,4 @@
 org.gradle.parallel=true
 archunit.group=com.tngtech.archunit
-archunit.version=1.3.0-SNAPSHOT
+archunit.version=1.2.1-SNAPSHOT
 org.gradle.jvmargs=--add-exports jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED --add-exports jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED --add-exports jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED --add-exports jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED --add-exports jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-exports jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED