Forbidden Apis fixed

Signed-off-by: Siddharth Rayabharam <maitreya2954@gmail.com>

server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregatorFactory.java

@@ -72,7 +72,7 @@ public static ExecutionMode fromString(String value) {
                 return UNSET;
             }
             try {
-                return ExecutionMode.valueOf(value.toUpperCase());
+                return ExecutionMode.valueOf(value.toUpperCase(Locale.ROOT));
             } catch (IllegalArgumentException e) {
                 throw new IllegalArgumentException("Unknown `execution_hint`: [" + value + "], expected any of [direct, ordinals]");
             }