CCM-24223: Add role policy attachment dependency for lambda

[sidnhs]

Description

We were getting race conditions with the aurora bootstrap lambda where the IAM role policy for the execution role was getting destroyed before teh lambda, leading to a series of half-destroyed PR envs e.g.:
https://github.com/NHSDigital/nhs-notify-internal/actions/runs/37965655660/job/113939779017

https://github.com/NHSDigital/nhs-notify-internal/actions/runs/38232045638/job/114754228314 - this seems to destroy cleanly

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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