Update OpenAPI Descriptions (#17476)

Author: github-openapi-bot

lib/rest/static/dereferenced/api.github.com.deref.json

@@ -55444,11 +55444,13 @@
                       },
                       "authorized_credential_title": {
                         "type": "string",
+                        "nullable": true,
                         "example": "my ssh key",
                         "description": "The title given to the ssh key. This will only be present when the credential is an ssh key."
                       },
                       "authorized_credential_note": {
                         "type": "string",
+                        "nullable": true,
                         "example": "my token",
                         "description": "The note given to the token. This will only be present when the credential is a token."
                       }