Need to mention the exact directory location to create password file for secure vault

[tharikaGitHub]

Description:
In the documentation [1], it is asked to create a new file either password-tmp or password-persist to get the passwords when running the APIM server as a background task. But the exact location that the file should be created is not mentioned. The location should be the root directory. <API-M_HOME>

[1] https://apim.docs.wso2.com/en/4.3.0/install-and-setup/setup/security/logins-and-passwords/working-with-encrypted-passwords/#start-server-as-a-background-job