Add missing Nullable annotation.

For one of constructor arguments of the AggregationOptions the Nullable annotation for the cursor argument is missing.

Closes: #4256

Author: soumyaPrakashB

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOptions.java

@@ -33,6 +33,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Yadhukrishna S Pai
+ * @author Soumya Prakash Behera
  * @see Aggregation#withOptions(AggregationOptions)
  * @see TypedAggregation#withOptions(AggregationOptions)
  * @since 1.6
@@ -65,7 +66,7 @@ public class AggregationOptions {
 	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
 	 * @param cursor can be {@literal null}, used to pass additional options to the aggregation.
 	 */
-	public AggregationOptions(boolean allowDiskUse, boolean explain, Document cursor) {
+	public AggregationOptions(boolean allowDiskUse, boolean explain, @Nullable Document cursor) {
 		this(allowDiskUse, explain, cursor, null);
 	}