add Scale and Priority to ServiceTier

[kczimm]

The new 3.1.0 spec added variants to the ServiceTier

        ServiceTier:
            type: string
            description: |
                Specifies the processing type used for serving the request.
                  - If set to 'auto', then the request will be processed with the service tier configured in the Project settings. Unless otherwise configured, the Project will use 'default'.
                  - If set to 'default', then the request will be processed with the standard pricing and performance for the selected model.
                  - If set to '[flex](https://platform.openai.com/docs/guides/flex-processing)' or '[priority](https://openai.com/api-priority-processing/)', then the request will be processed with the corresponding service tier.
                  - When not set, the default behavior is 'auto'.

                  When the `service_tier` parameter is set, the response body will include the `service_tier` value based on the processing mode actually used to serve the request. This response value may be different from the value set in the parameter.
            enum:
                - auto
                - default
                - flex
                - scale
                - priority
            nullable: true
            default: auto

[64bit]

Thank you for the update.