ES|QL: disable mixed cluster CSV tests that require source field mapping (#122607)

Author: luigidellaquila

x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/MixedClusterEsqlSpecIT.java

@@ -21,7 +21,6 @@
 
 import static org.elasticsearch.xpack.esql.CsvTestUtils.isEnabled;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V12;
-import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.SOURCE_FIELD_MAPPING;
 
 public class MixedClusterEsqlSpecIT extends EsqlSpecTestCase {
     @ClassRule
@@ -93,7 +92,7 @@ protected boolean supportsIndexModeLookup() throws IOException {
 
     @Override
     protected boolean supportsSourceFieldMapping() throws IOException {
-        return hasCapabilities(List.of(SOURCE_FIELD_MAPPING.capabilityName()));
+        return false;
     }
 
     @Override