docs(step-functions): modify description of itemReaderPath

**Why**
- the first line of comment is used as the description shown in the properties table, hence, repeating the property name does not convey much

**What**
- replace first line of comment from property name to description of property

**Tested by**
- `yarn build`

packages/aws-cdk-lib/aws-stepfunctions/lib/states/distributed-map.ts

@@ -37,8 +37,6 @@ export interface DistributedMapProps extends MapBaseProps {
   readonly itemReader?: IItemReader;
 
   /**
-   * ItemReaderPath
-   *
    * Configuration for where to read items dataset in S3 to iterate, as JsonPath
    *
    * @default - No itemReaderPath