remove duplicate content type setting

Author: Vignesh Kennadi

src/main/java/com/xero/api/client/AccountingApi.java

@@ -528,7 +528,6 @@ public HttpResponse createAccountAttachmentByFileNameForHttpResponse(
     HttpHeaders headers = new HttpHeaders();
     headers.set("xero-tenant-id", xeroTenantId);
     headers.set("Idempotency-Key", idempotencyKey);
-    headers.setContentType("application/octet-stream");
     headers.setAccept("application/json");
     headers.setContentType("application/octet-stream");
     headers.setUserAgent(this.getUserAgent());