add back the sdk version number

Author: tkhill-AWS

.doc_gen/metadata/dynamodb_metadata.yaml

@@ -1957,7 +1957,7 @@ dynamodb_Scenario_GettingStartedMovies:
                 - dynamodb.java2.scenario.main
     PHP:
       versions:
-        - sdk_version:
+        - sdk_version: 3
           github: php/example_code/dynamodb
           excerpts:
             - description: Because this example uses supporting files, be sure to <ulink url="https://github.com/awsdocs/aws-doc-sdk-examples/blob/main/php/README.md#prerequisites">read the guidance</ulink> in the PHP examples README.md file.