chore: pin to KIC helm 0.15.2 / image 2.4.2 due to #225

[qdzlug]

Proposed changes

This is a temp fix for #225 - it pins our NGINX Ingress helm chart to 0.15.2 and our NGINX binary to 2.4.2 if no other value exists in the pulumi configuration for that stack.

This will be reverted once the issues defined in #225 are mitigated.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have written my commit messages in the Conventional Commits format.
• I have read the CONTRIBUTING doc
• I have added tests (when possible) that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork

[4141done]

Looks good, my usual comment about the number of places this version number needs to be changed stands but I know we'll be addressing this in larger changes down the line.