Update information about scopes

Descriptions of scopes are different between the OAuth Doc and the API config page of production.

### Reference

- OAuth Doc [Using OAuth to Access Adobe Sign APIs](https://secure.jp1.echosign.com/public/static/oauthDoc.jsp)
- REST API Demo [REST API — Document e\-signature Software — Adobe Sign](https://secure.jp1.echosign.com/redirect/latestRestApiMethods)
- [Open API(github)](https://github.com/adobe-sign/AdobeSign-OpenAPI)
- [Adobe Sign API config page of production](https://secure.jp1.echosign.com/account/accountSettingsPage#pageId::API_APPLICATIONS)

### List of scopes

|Scope target | written in [OAuth Doc](https://secure.jp1.echosign.com/public/static/oauthDoc.jsp) | used in [Rest API Demo](https://secure.jp1.echosign.com/redirect/latestRestApiMethods) | used in [Open API(github)](https://github.com/adobe-sign/AdobeSign-OpenAPI) | exists in [API config page of production](https://secure.jp1.echosign.com/account/accountSettingsPage#pageId::API_APPLICATIONS)|
|---|:---:|:---:|:---:|:---:|
|agreement_sign | NO | YES | YES| NO|
|agreement_retention | YES | YES | YES | NO|
|agreement_vault | YES | YES | YES| NO |
|agreement_send | NO | YES | YES | YES|
|library_retention | NO | YES | YES | NO|
|account_read| NO | YES | NO | NO|

Review the OAuth Doc, REST API Demo, AdobeSign-OpenAPI repository, and production API config page listed in the issue. Compare the scope names and descriptions, then update the relevant documentation so the sources agree; done means the discrepancies in the scope table are resolved.

Written by the indexing model from the issue text.