fix: update authority url in confidential client

[aramase]

According to the function signature

// New is the constructor for Client. authority is the URL of a token authority such as "https://login.microsoftonline.com/<your tenant>".
// If the Client will connect directly to AD FS, use "adfs" for the tenant. clientID is the application's client ID (also called its
// "application ID").
func New(authority, clientID string, cred Credential, options ...Option) (Client, error) {

xref: https://github.com/AzureAD/microsoft-authentication-library-for-go/blob/v1.2.2/apps/confidential/confidential.go#L310-L313