chore: bump Spark 4.1 to 4.1.3

[andygrove]

Which issue does this PR close?

N/A — routine patch-version bump within the already-supported Spark 4.1 line.

Rationale for this change

Spark 4.1 support should track the latest Spark 4.1 patch release. Apache Spark
4.1.3 has been released (tag v4.1.3), so this moves Comet's Spark 4.1 build,
CI, Docker image, and documentation from 4.1.2 to 4.1.3. Spark 4.1 is also
Comet's default profile, so this bumps the top-level <spark.version> too.

What changes are included in this PR?

• Bumps the default <spark.version> and the spark-4.1 profile's
  <spark.version> to 4.1.3. Spark 4.1.3 makes no transitive dependency changes
  relative to 4.1.2 (scala.version 2.13.17, parquet.version 1.16.0,
  slf4j.version 2.0.17, jetty.version 11.0.26, hadoop.version 3.4.2,
  arrow.version 18.3.0 are all unchanged), so no other profile properties move
  and spark/pom.xml's pinned Jetty 11.0.26 test deps still match — only the
  comment naming the reference version is updated.
• Renames dev/diffs/4.1.2.diff to dev/diffs/4.1.3.diff and regenerates it
  against the v4.1.3 tag. Two hunks needed manual reapplication, both pure
  import-line context drift with no behavioural change:
  • DataFrameWindowFunctionsSuite.scala — upstream added a
    catalyst.trees.UnaryLike import between the patched neighbours.
  • StreamRealTimeModeAllowlistSuite.scala — upstream moved
    LowLatencyMemoryStream from execution.streaming to
    execution.streaming.sources.
• Points the Spark SQL, Spark SQL writer, Iceberg 1.11, and PyArrow UDF CI jobs
  at 4.1.3, and updates dev/ci/compute-changes.py's spark_4_1 path filter to
  the new diff filename.
• Bumps kube/Dockerfile to apache/spark:4.1.3 and updates the Kubernetes,
  macOS benchmarking, installation, compatibility, and Iceberg docs.

How are these changes tested?

• git apply --check dev/diffs/4.1.3.diff against a pristine v4.1.3 checkout
  passes with no rejects or fuzz.
• Verified the regenerated diff touches exactly the same 96 files as the 4.1.2
  diff, and that its only content differences from 4.1.2 are the two context
  lines above.
• npx prettier --check on the modified markdown.
• Full verification is the Spark SQL and Iceberg 1.11 CI jobs on this PR, which
  clone v4.1.3, apply the new diff, and run the test suites.

One thing to confirm on review

Maven Central, PyPI, and Docker Hub are all unreachable from the environment I
prepared this in, so I could not independently confirm that the
org.apache.spark:*:4.1.3 artifacts, pyspark==4.1.3, and the
apache/spark:4.1.3 image are all published yet — the v4.1.3 tag (identical to
v4.1.3-rc1, i.e. the vote passed on rc1) is the only evidence I could gather.
CI will fail fast on the Maven and PyPI pins if either is not yet available. The
apache/spark Docker image sometimes lags the release, and kube/Dockerfile is
not exercised by CI, so that tag is worth an explicit check before merge.

[mbutrovich]

Approved pending CI, thanks @andygrove!