fix: Correct 2nd reference

Author: bryantbiggs

main.tf

@@ -439,7 +439,7 @@ resource "aws_cloudfront_distribution" "this" {
 
         content {
           event_type   = f.key
-          function_arn = lookup(f.value, "function_arn", try(aws_cloudfront_function.this[lookup(f.value, "function_name", "")].arn, null))
+          function_arn = lookup(f.value, "function_arn", try(aws_cloudfront_function.this[f.value.function_key].arn, null))
         }
       }