Well, I would suggest to reach out to the IaC Git project to ask this question.
What I take: this is a warning and should not be an error, unless your terraform script/call has a flag to consider warnings as errors, it should continue well as it is renaming the variable & just notifying.
Assuming your CIDRs are correct and not the root cause, you can also:
- you can go ahead and change the variable in the script by yourself
- check the provider that is being used and the version