Fixed incorrectly named variable in the for loop which deletes legacy…

[waltmayfield]

… domains

Issue #, if available:
Deleting legacy domains would fail b/c the delete_domain_cicd_stack function was given an incorrectly named domain variable.
for legacy_domain in legacy_domains:
stack_details = delete_domain_cicd_stack(domain, environment, cloudformation_role)

Here's the error you get when triggering the delete_domain_cicd_stack funciton from the for loop:
[ERROR] UnboundLocalError: cannot access local variable 'domain' where it is not associated with a value
Traceback (most recent call last):
File "/var/task/lambda_function.py", line 247, in lambda_handler
stack_details = delete_domain_cicd_stack(domain, environment, cloudformation_role)

Description of changes:
I changed domain to legacy_domain in the delete_domain_cicd_stack argument.
Also my Amazon email address is [email protected]. Would love to contribute to this project!

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[cnfait]

Thank you!