-pr http11 flag is ignored on retryablehttp-go due to HTTP/2 fallback

[khs-alt]

Versions

• httpx: v1.7.1
• retryablehttp-go: v1.0.119

Current Behavior:

If you see httpx repocommon/httpx/httpx.go 156 line

	if httpx.Options.Protocol == "http11" {
		// disable http2
		os.Setenv("GODEBUG", "http2client=0")
		transport.TLSNextProto = map[string]func(string, *tls.Conn) http.RoundTripper{}
	}

When using HTTP 1.1, change transport, and it will use retryablehttp
But if we see retryablehttp repo do.go 62 line

		// if err is equal to missing minor protocol version retry with http/2
		if err != nil && stringsutil.ContainsAny(err.Error(), "net/http: HTTP/1.x transport connection broken: malformed HTTP version \"HTTP/2\"", "net/http: HTTP/1.x transport connection broken: malformed HTTP response") {
			resp, err = c.HTTPClient2.Do(req.Request)
			checkOK, checkErr = c.CheckRetry(req.Context(), resp, err)
		}

This issue is caused by the retry behavior in retryablehttp-go, as discussed in
projectdiscovery/retryablehttp-go#3.
If httpx set client for using only http1.1 but retryable use another client in this case so -pr does not work correctly.

Expected Behavior:

Use transport change client when httpx -pr is on

Suggestion

Add Options.DisableHTTPFallback (Example). If set, skip the HTTP/2 fallback (HTTPClient2) on malformed HTTP/2 errors and treat them according to the retry policy.
This respects explicit HTTP/1.1-only configs and avoids unintended protocol switches and policy divergence (proxy/dialer/redirect/TLS)