Bump org.apache.iceberg:iceberg-bom from 1.7.1 to 1.8.1 (#529)

Bumps [org.apache.iceberg:iceberg-bom](https://github.com/apache/iceberg) from 1.7.1 to 1.8.1.
- [Release notes](https://github.com/apache/iceberg/releases)
- [Commits](apache/iceberg@apache-iceberg-1.7.1...apache-iceberg-1.8.1)

---
updated-dependencies:
- dependency-name: org.apache.iceberg:iceberg-bom
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pom.xml

@@ -35,7 +35,7 @@
         <skipITs>true</skipITs>
 
         <!-- Iceberg -->
-        <version.iceberg>1.7.1</version.iceberg>
+        <version.iceberg>1.8.1</version.iceberg>
         <!-- Following two properties defines which version of iceberg-spark-runtime is used -->
         <!-- Example https://mvnrepository.com/artifact/org.apache.iceberg/iceberg-spark-runtime-3.4_2.13/1.4.3 -->
         <version.spark.major>4.0</version.spark.major>