fix(analytics): remove ad_impression from reserved events

[alexpovkolas]

Description

Related issues

Fixes #6307

Release Summary

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

---

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Name	Status	Preview	Updated
react-native-firebase	✅ Ready (Inspect)	Visit Preview	Jun 15, 2022 at 9:52AM (UTC)

1 Ignored Deployment

Name	Status	Preview	Updated
react-native-firebase-next	⬜️ Ignored (Inspect)		Jun 15, 2022 at 9:52AM (UTC)

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[mikehardy]

nice - thank you! Even for small things we need the CLA signed but code wise, of course (since it is a simple change) it looks good...

[codecov]

Codecov Report

Merging #6312 (58e12cd) into main (ee740f8) will increase coverage by 18.88%.
The diff coverage is n/a.

❗ Current head 58e12cd differs from pull request most recent head 216fe40. Consider uploading reports for the commit 216fe40 to get more accurate results

@@              Coverage Diff              @@
##               main    #6312       +/-   ##
=============================================
+ Coverage     53.42%   72.30%   +18.88%     
=============================================
  Files           208      109       -99     
  Lines         10315     4649     -5666     
  Branches       1633     1046      -587     
=============================================
- Hits           5510     3361     -2149     
+ Misses         4547     1210     -3337     
+ Partials        258       78      -180     

[mikehardy]

CLA missing and lint needs some help. #6314 will implement this