fix: remove duplicate Content-Type header in update_record

`.json(&body)` already sets the header.
the explicit `.header()` appended a second value.
the duplicate caused GoDaddy to reject wildcard updates.

src/godaddy/mod.rs

@@ -23,7 +23,6 @@ pub async fn update_record(record: DNSRecord, auth: &Auth) -> () {
         .patch(api.to_string())
         .json(&body)
         .header("accept", "application/json")
-        .header("content-type", "application/json")
         .header("authorization", &header);
     debug!("{:?}", api.to_string());