main: Update dependency org.apache.spark:spark-sql_2.12 to v3.5.6 (#1794)

Author: renovate-bot

integration-tests/build.gradle.kts

@@ -53,7 +53,7 @@ dependencies {
 
   implementation("org.apache.iceberg:iceberg-spark-3.5_2.12")
   implementation("org.apache.iceberg:iceberg-spark-extensions-3.5_2.12")
-  implementation("org.apache.spark:spark-sql_2.12:3.5.5") {
+  implementation("org.apache.spark:spark-sql_2.12:3.5.6") {
     // exclude log4j dependencies
     exclude("org.apache.logging.log4j", "log4j-slf4j2-impl")
     exclude("org.apache.logging.log4j", "log4j-api")