Update Rust and Ruby DynamoDB examples to use on-demand rather than provisioned

Author: brmur

ruby/example_code/dynamodb/README.md

@@ -104,7 +104,7 @@ This example shows you how to do the following:
 Start the example by running the following at a command prompt:
 
 ```
-ruby ./basics/scenario_getting_started_dynamodb.rb
+ruby scaffold.rb
 ```
 
 <!--custom.basics.dynamodb_Scenario_GettingStartedMovies.start-->
@@ -184,4 +184,4 @@ To learn more about the contributing process, see [CONTRIBUTING.md](../../../CON
 
 Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 
-SPDX-License-Identifier: Apache-2.0
+SPDX-License-Identifier: Apache-2.0

ruby/example_code/dynamodb/scaffold.rb

@@ -68,7 +68,7 @@ def create_table(table_name)
         { attribute_name: 'year', attribute_type: 'N' },
         { attribute_name: 'title', attribute_type: 'S' }
       ],
-      billing_mode: "PAY_PER_REQUEST"
+      billing_mode: 'PAY_PER_REQUEST'
     )
     @dynamo_resource.client.wait_until(:table_exists, table_name: table_name)
     @table