Fix documentation for HiveConfig hive.s3.use-instance-credentials (fa…

…cebookincubator#8309)

Summary:
The default value is false.
https://github.com/facebookincubator/velox/blob/005e5457d146ab42b0ad421f902853b441b11ea7/velox/connectors/hive/HiveConfig.cpp#L93

Pull Request resolved: facebookincubator#8309

Reviewed By: Yuhta

Differential Revision: D52638429

Pulled By: kgpai

fbshipit-source-id: f9b54adc6e7b6e9e763ca6c9a0e38c3c8cb54f11

velox/docs/configs.rst

@@ -496,7 +496,7 @@ Each query can override the config by setting corresponding query session proper
      - Description
    * - hive.s3.use-instance-credentials
      - bool
-     - true
+     - false
      - Use the EC2 metadata service to retrieve API credentials. This works with IAM roles in EC2.
    * - hive.s3.aws-access-key
      - string