Ask to use CalciteCrossClusterSearchIT when developing calcite-only commands

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

docs/dev/ppl-commands.md

@@ -52,7 +52,7 @@ If you are working on contributing a new PPL command, please read this guide and
   - Add a test in `PPLQueryDataAnonymizerTest`
 
 - [ ] **Cross-cluster Tests (optional, nice to have):**
-  - Add a test in `CrossClusterSearchIT`
+  - Add a test in `CrossClusterSearchIT`, or in `CalciteCrossClusterSearchIT` if the command requires Calcite.
 
 - [ ] **User doc:**
   - Add a xxx.md under `docs/user/ppl/cmd` and link the new doc to `docs/user/ppl/index.md`

integ-test/src/test/java/org/opensearch/sql/security/CalciteCrossClusterSearchIT.java

@@ -352,7 +352,6 @@ public void testCrossClusterRexWithOffsetField() throws IOException {
 
   @Test
   public void testCrossClusterAddTotals() throws IOException {
-    // Test query_string without fields parameter on remote cluster
     JSONObject result =
         executeQuery(
             String.format(
@@ -364,7 +363,6 @@ public void testCrossClusterAddTotals() throws IOException {
   /** CrossClusterSearchIT Test for addcoltotals. */
   @Test
   public void testCrossClusterAddColTotals() throws IOException {
-    // Test query_string without fields parameter on remote cluster
     JSONObject result =
         executeQuery(
             String.format(
@@ -377,7 +375,6 @@ public void testCrossClusterAddColTotals() throws IOException {
 
   @Test
   public void testCrossClusterTranspose() throws IOException {
-    // Test query_string without fields parameter on remote cluster
     JSONObject result =
         executeQuery(
             String.format(