fix: keep mailgun version the same

Author: jonathanedey

.github/actions/send-email/package-lock.json

@@ -15,7 +15,7 @@
   "license": "Apache-2.0",
   "dependencies": {
     "@actions/core": "^1.10.1",
-    "mailgun.js": "^3.7.3"
+    "mailgun.js": "^3.3.0"
   },
   "devDependencies": {
     "@vercel/ncc": "^0.38.1"