feat: Correct enable_mfa_enforcement spelling

[booi]

Description

correct spelling of the enable_mfa_enforcement option in iam-group-with-policies

Motivation and Context

Fixes #377
Closes #401

Breaking Changes

yes, anybody with the old spelling enable_mfa_enforcment will be required to update their code to the new option.

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

• [ X ] I have executed pre-commit run -a on my pull request

Terraform fmt............................................................Passed
Terraform wrapper with for_each in module................................Passed
Terraform validate.......................................................Passed
Terraform docs...........................................................Passed
Terraform validate with tflint...........................................Passed
check for merge conflicts................................................Passed
fix end of files.........................................................Passed

[antonbabenko]

This PR is included in version 5.27.0 🎉

[github-actions]

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