infra: spark 4 already comes with spark connect jar (apache#2887)

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# Rationale for this change
Check against the `apache/spark:4.0.1` image. Save a couple MBs of
download :D

```
➜  iceberg-python git:(main) docker run --rm apache/spark:4.0.1 ls -la /opt/spark/jars | grep -i c
onnect
Unable to find image 'apache/spark:4.0.1' locally
4.0.1: Pulling from apache/spark
fdf67ba0bcdc: Already exists 
33c2d1bf8782: Already exists 
9a562fdfee59: Already exists 
b6953a5f4a05: Already exists 
c00fd4799efc: Already exists 
bf65a9815f44: Already exists 
df261ba86031: Already exists 
986913f619c8: Already exists 
9c58c89601af: Already exists 
4f4fb700ef54: Already exists 
9da5037c6883: Already exists 
Digest: sha256:acfe7e06e95dd13aa32ee03c464766900d52fba15f58e421f8e1213ec041bb94
Status: Downloaded newer image for apache/spark:4.0.1
drwxr-xr-x 1 spark spark     2330 Sep  2 03:39 connect-repl
-rw-r--r-- 1 spark spark 16577649 Sep  2 03:39 spark-connect_2.13-4.0.1.jar
```

## Are these changes tested?

## Are there any user-facing changes?

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Author: kevinjqliu

dev/spark/Dockerfile

@@ -20,7 +20,6 @@ FROM apache/spark:${BASE_IMAGE_SPARK_VERSION}
 # Dependency versions - keep these compatible
 ARG ICEBERG_VERSION=1.10.1
 ARG ICEBERG_SPARK_RUNTIME_VERSION=4.0_2.13
-ARG SPARK_VERSION=4.0.1
 ARG HADOOP_VERSION=3.4.1
 ARG SCALA_VERSION=2.13
 ARG AWS_SDK_VERSION=2.24.6
@@ -43,7 +42,6 @@ RUN mkdir -p /home/iceberg/spark-events && \
 
 # Required JAR dependencies
 ENV JARS_TO_DOWNLOAD="\
-    org/apache/spark/spark-connect_${SCALA_VERSION}/${SPARK_VERSION}/spark-connect_${SCALA_VERSION}-${SPARK_VERSION}.jar \
     org/apache/iceberg/iceberg-spark-runtime-${ICEBERG_SPARK_RUNTIME_VERSION}/${ICEBERG_VERSION}/iceberg-spark-runtime-${ICEBERG_SPARK_RUNTIME_VERSION}-${ICEBERG_VERSION}.jar \
     org/apache/iceberg/iceberg-aws-bundle/${ICEBERG_VERSION}/iceberg-aws-bundle-${ICEBERG_VERSION}.jar \
     org/apache/hadoop/hadoop-aws/${HADOOP_VERSION}/hadoop-aws-${HADOOP_VERSION}.jar \