Add --offline flag to update tool documentation

[Aaquiff]

Description: Location: https://updates.docs.wso2.com/en/latest/updates/update-tool

We need to add the flag --offline to the flags list for apply-hotfix command.

--offline apply hotfix offline

• https://updates.docs.wso2.com/en/latest/updates/update-commands/#wso2update_os62-apply-hotfix

[chamindi-a]

Duplicate of #88

[chamindi-a]

This content is changed thus the issue is fixed