Fix setting HTTP headers after write (#21833)

The headers can't be modified after it was send to the client.

routers/web/feed/profile.go

@@ -5,7 +5,6 @@
 package feed
 
 import (
-	"net/http"
 	"time"
 
 	activities_model "code.gitea.io/gitea/models/activities"
@@ -59,7 +58,6 @@ func showUserFeed(ctx *context.Context, formatType string) {
 
 // writeFeed write a feeds.Feed as atom or rss to ctx.Resp
 func writeFeed(ctx *context.Context, feed *feeds.Feed, formatType string) {
-	ctx.Resp.WriteHeader(http.StatusOK)
 	if formatType == "atom" {
 		ctx.Resp.Header().Set("Content-Type", "application/atom+xml;charset=utf-8")
 		if err := feed.WriteAtom(ctx.Resp); err != nil {