build: go 1.24

We were running behind and there were quite some deprecations to update.
This was mostly in the upstream copy/pasta package but seems quite
minimal.

vendor/golang.org/x/net/http2/write.go

@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/net/http/httpguts"
 	"golang.org/x/net/http2/hpack"
+	"golang.org/x/net/internal/httpcommon"
 )
 
 // writeFramer is implemented by any type that is used to write frames.
@@ -351,7 +352,7 @@ func encodeHeaders(enc *hpack.Encoder, h http.Header, keys []string) {
 	}
 	for _, k := range keys {
 		vv := h[k]
-		k, ascii := lowerHeader(k)
+		k, ascii := httpcommon.LowerHeader(k)
 		if !ascii {
 			// Skip writing invalid headers. Per RFC 7540, Section 8.1.2, header
 			// field names have to be ASCII characters (just as in HTTP/1.x).