chore: replace security-header-lambda with native cloudfront responseheaderpolicy

[joshbalfour]

needs testing on dev

unit test fail is due to cognito-custom-mailer coverage so unrelated

[rpt-uk-github]

:tada: Snyk checks have passed. No issues have been found so far.

:white_check_mark: security/snyk check is complete. No issues have been found. (View Details)

:white_check_mark: license/snyk check is complete. No issues have been found. (View Details)

:white_check_mark: code/snyk check is complete. No issues have been found. (View Details)

[bashleigh]

Feel free to tell me where to go 😅 should we make it consistent, like you have or make it a construct to future proof it. Sorry in advance