MINOR: h3: remove duplicated FIN flag position

The FIN flag is already set in h3_snd_buf on HTX EOM reception. The same
action in h3_resp_headers_send is duplicated and thus now removed.
diff --git a/src/h3.c b/src/h3.c
index 14c56c6..6414c59 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -484,9 +484,6 @@
 			break;
 	}
 
-	if ((htx->flags & HTX_FL_EOM) && htx_is_empty(htx) && status >= 200)
-		qcs->flags |= QC_SF_FIN_STREAM;
-
 	return ret;
 
  err: