fix: do not send any mock exposure data when leadTime > 3 months

[jannisvisser]

Describe your changes

Resolves bug 859

Checklist before requesting a review

• I have performed a self-review of my code
• I have added tests wherever relevant
• I have made sure that all automated checks pass before requesting a review

Notes for the reviewer

1. I basically reversed the previous edit on this same line of code, which was - according to the commit message - done to fix ZWE mock. But this code is within an IF, which specifically excludes ZWE.
2. So I reversed it and checked both for Ethiopia (fixes the bug) and for Zimbabwe (still works fine).
3. This is a mock only bug. Production pipeline should take care of not sending any data for more than 3 months leadTime.