Small update

Signed-off-by: Craig Perkins <cwperx@amazon.com>

src/test/kotlin/org/opensearch/indexmanagement/indexstatemanagement/IndexStateManagementRestTestCase.kt

@@ -342,7 +342,7 @@ abstract class IndexStateManagementRestTestCase : IndexManagementRestTestCase()
         val res =
             adminClient().makeRequest(
                 "PUT", "$index/_settings", emptyMap(),
-                StringEntity(body, ContentType.APPLICATION_JSON),
+                StringEntity(body, APPLICATION_JSON),
             )
         assertEquals("Update index setting failed", RestStatus.OK, res.restStatus())
     }