fix: remove ping command not available in Maven container

The maven:3.9-eclipse-temurin-17 image doesn't include ping utility.
DNS resolution was already confirmed working in previous runs.
Remove diagnostic ping commands - not needed anymore.

test/java/spark/docker-compose.yml

@@ -83,7 +83,7 @@ services:
       - MAVEN_OPTS=-Dsun.net.inetaddr.ttl=0 -Dnetworkaddress.cache.ttl=0
       # Force fsync on close to ensure data is flushed before file is considered written
       - SPARK_SUBMIT_OPTS=-Dfs.seaweedfs.impl.disable.cache=true
-    command: sh -c "sleep 30 && ping -c 1 seaweedfs-volume && ping -c 1 seaweedfs-filer && mvn test"
+    command: sh -c "sleep 30 && mvn test"
     depends_on:
       seaweedfs-filer:
         condition: service_healthy