chore: bump dependency on iso8601_timestamp

[novacrazy]

Reposting this here for you:

Before:

// ...
expiry: Timestamp::from_unix_timestamp_ms(
    chrono::Utc::now()
        .checked_add_signed(Duration::seconds(expiry.expire_verification))
        .expect("failed to checked_add_signed")
        .timestamp_millis(),
),

After:

use iso8601_timestamp::{Timestamp, Duration};
// ...
expiry: Timestamp::now_utc()
    .checked_add(Duration::seconds(expiry.expire_verification))
    .expect("failed to checked_add"),