update endpoint description

Author: mfori

apify-api/openapi/paths/datasets/datasets@{datasetId}@field-statistics.yaml

@@ -4,7 +4,7 @@ get:
   summary: Get field statistics
   description: |
     Returns field statistics for given dataset.
-    When you configure the dataset [fields schema](https://docs.apify.com/platform/actors/development/actor-definition/dataset-schema/validation), we generate a field list and measure the statistics such as `min`, `max`, `nullCount` and `emptyCount`.
+    When you configure the dataset [fields schema](https://docs.apify.com/platform/actors/development/actor-definition/dataset-schema/validation), we measure the statistics such as `min`, `max`, `nullCount` and `emptyCount` for each field.
 
     See dataset fields schema [documentation](https://docs.apify.com/platform/actors/development/actor-definition/dataset-schema/validation#dataset-field-statistics) for more information.