Remove doc from the path (#3043)

```
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.8.0:jar (module-javadocs) on project avro-idl: MavenReportException: Error while generating Javadoc: 
[ERROR] Exit code: 2
[ERROR] error: No source files for package org.apache.avro.util
[ERROR] 1 error
[ERROR] Command line was: /usr/lib/jvm/java-21-openjdk-arm64/bin/javadoc -J-Duser.language= -J-Duser.country= -Xdoclint:none @options @packages
[ERROR] 
[ERROR] Refer to the generated Javadoc files in '/home/fokko.driesprong/avro/lang/java/idl/target/apidocs' dir.
[ERROR] 
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
[ERROR] 
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <args> -rf :avro-idl
```

pom.xml

@@ -589,7 +589,7 @@
                   <fileset dir="lang/java/target/site/apidocs"/>
                 </copy>
                 <copy todir="build/avro-doc-${project.version}/trevni">
-                  <fileset dir="lang/java/trevni/doc/target/site"/>
+                  <fileset dir="lang/java/trevni/target/site"/>
                 </copy>
               </target>
             </configuration>