Remove Heap code

[PeterBreen]

DemocracyLab used to use Heap for analytics, but no longer - so all Heap-related code should be removed.

• remove all instances/uses of of HEAP_ANALYTICS_ID
• remove heapApi.js from 'common/components/utils'

We are likely to refactor our metrics utility for GA4, so please do not delete or remove the metrics.js / associated logging functions.

Then, smoke test the site to make sure render isn't blocked by the removal of heap.

Note for code reviewer: After this code is deployed,

• remove the HEAP_ANALYTICS_ID key on all environments
• remove Heap-related CSP entries. #738 for reference.

[sp6370]

Hi @PeterBreen! Can I pick this up?

[PeterBreen]

Yes, please! I've assigned you. Feel free to reach out on github or slack if you've got any questions.

[sp6370]

@PeterBreen Apologies for the delay. I have opened a new pull request,