Increase S3 connection in Iceberg MinIO tests

The limit was decreased in a33044e, but
it's too low. It's causing a congestion when working with Iceberg manifest
files during optimize. Revert it back to the previous value.

plugin/trino-iceberg/src/test/java/io/trino/plugin/iceberg/TestIcebergMinioOrcConnectorTest.java

@@ -72,7 +72,7 @@ protected QueryRunner createQueryRunner()
                                 .put("s3.endpoint", minio.getMinioAddress())
                                 .put("s3.path-style-access", "true")
                                 .put("s3.streaming.part-size", "5MB") // minimize memory usage
-                                .put("s3.max-connections", "2") // verify no leaks
+                                .put("s3.max-connections", "8") // verify no leaks
                                 .put("iceberg.register-table-procedure.enabled", "true")
                                 // Allows testing the sorting writer flushing to the file system with smaller tables
                                 .put("iceberg.writer-sort-buffer-size", "1MB")