Downgrade build-helper-maven-plugin to 3.4.0 to fix JitPack build

Author: vojtapol

Diff for: pom.xml

@@ -240,7 +240,7 @@
             <plugin>
                 <groupId>org.codehaus.mojo</groupId>
                 <artifactId>build-helper-maven-plugin</artifactId>
-                <version>3.5.0</version>
+                <version>3.4.0</version>
                 <executions>
                     <execution>
                         <id>add-test-source</id>