Stop sending the Accept-Charset headers

We currently send this header when creating new curl requests if no headers were specified. We shoudn't.

It has been deprecated and should not be used any more:
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Charset

Warning: Do not use this header. Browsers omit this header and servers should ignore it.

Warning: Do not use this header. Browsers omit this header and servers should ignore it.

The Accept-Charset request HTTP header was a header that advertised a client's supported character encodings. It is no longer widely used.

UTF-8 is well-supported and the overwhelmingly preferred choice for character encoding. To guarantee better privacy through less configuration-based entropy, all browsers omit the Accept-Charset header.