[VL] Decouple iceberg-test and backends-velox profile in spotless check

### Description

When packaging for Velox backends with Spark-4.0, it seems iceberg-test profile for Spark-34 is also checked in spotless plugin:

https://github.com/apache/incubator-gluten/actions/runs/20373931796/job/58548066284

```
[INFO] Gluten Backends Velox .............................. FAILURE [ 4.904 s]
[INFO] Gluten Package ..................................... SKIPPED
[INFO] Gluten Ras Planner ................................. SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 05:13 min
[INFO] Finished at: 2025-12-19T15:20:14Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.44.2:check (spotless-check) on project backends-velox: The following files had format violations:
[ERROR] src-iceberg-spark34/test/java/org/apache/iceberg/spark/source/TestIcebergSourceTablesBase.java
[ERROR] @@ -1995,8 +1995,13 @@
[ERROR] ????????.save(loadLocation(tableIdentifier));
[ERROR]
[ERROR] ????List?actual?=
[ERROR] -????????spark.read().format("iceberg").load(loadLocation(tableIdentifier,?"files"))
[ERROR] -????????????.sort(DataFile.SPEC_ID.name()).collectAsList().stream()
[ERROR] +????????spark
[ERROR] +????????????.read()
[ERROR] +????????????.format("iceberg")
[ERROR] +????????????.load(loadLocation(tableIdentifier,?"files"))
[ERROR] +????????????.sort(DataFile.SPEC_ID.name())
[ERROR] +????????????.collectAsList()
[ERROR] +????????????.stream()
[ERROR] ????????????.map(r?->?(Integer)?r.getAs(DataFile.SPEC_ID.name()))
[ERROR] ????????????.collect(Collectors.toList());
[ERROR]
[ERROR] Run 'mvn spotless:apply' to fix these violations.
```

### Gluten version

None

Inspect the Maven Spotless configuration for the backends-velox and iceberg-test/Spark-34 profiles, then reproduce the failure with the affected packaging command. Use src-iceberg-spark34/test/java/org/apache/iceberg/spark/source/TestIcebergSourceTablesBase.java and the reported spotless:check output as references. Done means the backends-velox profile no longer checks the unrelated iceberg-test sources and its Spotless check passes.

Written by the indexing model from the issue text.