maven-source-plugin: downgrade to 3.2.1

Apparently it brreaks stuff, need to investigate that later.

Signed-off-by: Tom Siewert <[email protected]>

pom.xml

@@ -137,7 +137,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
-                <version>3.3.0</version>
+                <version>3.2.1</version>
                 <executions>
                     <execution>
                         <id>attach-sources</id>