chore(deps): pin dependency express to 4.21.2

Author: renovate[bot]

package.json

@@ -24,7 +24,7 @@
     "postversion": "git push"
   },
   "resolutions": {
-    "express": "^4.21.2"
+    "express": "4.21.2"
   },
   "dependencies": {
     "@actions/core": "1.11.1",

yarn.lock

@@ -1970,7 +1970,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"express@npm:^4.21.2":
+"express@npm:4.21.2":
   version: 4.21.2
   resolution: "express@npm:4.21.2"
   dependencies: