fix: upgrade spark version (apache#1384)

## Which issue does this PR close?

3.5.5 in https://dlcdn.apache.org/spark/ has been upgrade to 3.5.6

## What changes are included in this PR?

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## Are these changes tested?

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Co-authored-by: ZENOTME <st810918843@gmail.com>

Author: ZENOTME

crates/integration_tests/testdata/spark/Dockerfile

@@ -27,7 +27,7 @@ ENV PYTHONPATH=$SPARK_HOME/python:$SPARK_HOME/python/lib/py4j-0.10.9.7-src.zip:$
 RUN mkdir -p ${HADOOP_HOME} && mkdir -p ${SPARK_HOME} && mkdir -p /home/iceberg/spark-events
 WORKDIR ${SPARK_HOME}
 
-ENV SPARK_VERSION=3.5.5
+ENV SPARK_VERSION=3.5.6
 ENV ICEBERG_SPARK_RUNTIME_VERSION=3.5_2.12
 ENV ICEBERG_VERSION=1.6.0