DOCSP-11259 Relax to S3 region requirement (#48)

Author: kanchana-mongodb

source/reference/pipeline/out.txt

@@ -157,8 +157,10 @@ Fields
 
          * - ``s3.region``
            - string
-           - Name of the |aws| region in which the bucket is hosted.
-           - Required
+           - Name of the |aws| region in which the bucket is hosted. If 
+             omitted, uses the {+dl+} :ref:`configuration <datalake-configuration-file>` to determine the region where the 
+             specified ``s3.bucket`` is hosted.
+           - Optional
 
          * - ``s3.filename``
            - string
@@ -309,7 +311,7 @@ Examples
       .. example::
 
          You want to write 1 GiB of data as compressed |bson| files to
-         an |s3| bucket named ``my-s3-bucket``.
+         an |s3| bucket named ``my-s3-bucket``. 
 
          Using the following |out| syntax:
 
@@ -320,7 +322,6 @@ Examples
               "$out": {
                 "s3": {
                   "bucket": "my-s3-bucket",
-                  "region": "us-east-1",
                   "filename": "big_box_store/",
                   "format": {
                     "name": "bson.gz"
@@ -329,7 +330,9 @@ Examples
               }
             }
 
-         |out| writes five compressed |bson| files:
+         The ``s3.region`` is omitted and so, {+dl+} determines the 
+         region where the bucket named ``my-s3-bucket`` is hosted from the 
+         storage configuration. |out| writes five compressed |bson| files:
 
          1. The first 200 MiB of data to a file that |out| names
             ``big_box_store/1.bson.gz``.