build/pom: fix `shade` warning by excluding `com/alibaba/ttl3/agent/package-info` file
build/pom: fix `shade` warning by excluding `com/alibaba/ttl3/agent/package-info` file

[INFO] Dependency-reduced POM written at: .../ttl-agent/dependency-reduced-pom.xml
[WARNING] ttl-agent-3.x-SNAPSHOT.jar, ttl-core-3.x-SNAPSHOT.jar define 1 overlapping classes:
[WARNING]   - com.alibaba.ttl3.agent.package-info
[WARNING] maven-shade-plugin has detected that some class files are
[WARNING] present in two or more JARs. When this happens, only one
[WARNING] single version of the class is copied to the uber jar.

alibaba/transmittable-thread-local,alibaba/transmittable-thread-local,alibaba/transmittable-thread-local