appview/repo: avoid copying body in blob responses

Signed-off-by: oppiliappan <[e-mail]>

appview/repo/blob.go

···
 
 	if resp.StatusCode != http.StatusOK {
 		l.Error("knotserver returned non-OK status for raw blob", "url", blobURL, "statuscode", resp.StatusCode)
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 		w.WriteHeader(resp.StatusCode)
-		_, _ = io.Copy(w, resp.Body)
 		return
 	}