Fetch should ignore unsolicited 100 Continue responses #5899

I understand that Undici doesn't support the HTTP/1.1 Expect: 100-continue handshake. However, RFC 9110 §15.2.1 explicitly permits discarding a 100 Continue response when no expectation was sent.

In my own Playwright tests, Chromium, Firefox and WebKit continued to the final response, while Undici closed the connection. The README also says these responses are ignored.