Fix Writable Warm test for feature flag disabled condition by changin…

…g exception type caught

Signed-off-by: Shreyansh Ray <rayshrey@amazon.com>

server/src/internalClusterTest/java/org/opensearch/remotestore/WritableWarmIT.java

@@ -80,7 +80,7 @@ public void testWritableWarmFeatureFlagDisabled() {
         try {
             prepareCreate(INDEX_NAME).setSettings(indexSettings).get();
             fail("Should have thrown Exception as setting should not be registered if Feature Flag is Disabled");
-        } catch (SettingsException ex) {
+        } catch (SettingsException | IllegalArgumentException ex) {
             assertEquals(
                 "unknown setting ["
                     + IndexModule.INDEX_STORE_LOCALITY_SETTING.getKey()