Remove duplicated methods (`getSchemaRequested()` and `getSchemaResponse()`)

[sabina-talipova]

Description

Remove duplicated methods ContentReviewCMSExtension::getSchemaRequested() and ContentReviewCMSExtension::getSchemaResponse() once this issue will be released.

See:

• silverstripe-contentreview/src/Extensions/ContentReviewCMSExtension.php

  Line 132 in a7e77a6

  * @todo Remove duplication. See https://github.com/silverstripe/silverstripe-admin/issues/240

• silverstripe-contentreview/src/Extensions/ContentReviewCMSExtension.php

  Line 145 in a7e77a6

  * @todo Remove duplication. See https://github.com/silverstripe/silverstripe-admin/issues/240