Revert "remove variable definition"

This reverts commit 2ba2c15.

Author: devksingh4

terraform/modules/frontend/main.tf

@@ -220,7 +220,8 @@ resource "aws_cloudfront_function" "origin_key_injection" {
   runtime = "cloudfront-js-2.0"
   code    = <<EOT
 function handler(event) {
-    event.request.headers['x-origin-verify'] = { value: "${var.OriginVerifyKey}" };
+    var request = event.request;
+    request.headers['x-origin-verify'] = { value: "${var.OriginVerifyKey}" };
     return request;
 }
 EOT