Update the latest release tag to 1.39.4 (#398)

diff --git a/emscripten-releases-tags.txt b/emscripten-releases-tags.txt
index f64afec..fecfb5a 100644
--- a/emscripten-releases-tags.txt
+++ b/emscripten-releases-tags.txt
@@ -1,5 +1,5 @@
 {
-  "latest": "1.39.3",
+  "latest": "1.39.4",
   "releases": {
     "1.39.4":  "8bb7b0bbbca74cc58741416cc955011f22ff5ccb",
     "1.39.3":  "b024b71038d1291ed7ec23ecd553bf2c0c8d6da6",