docs(remote-config): error param for onConfigUpdated may be undefined but not null

[JasonPan]

Description

Minor fix for docs - the error param cannot be null, should be checking for undefined. The e2e tests confirm this behaviour.

I thought something else in my code was wrong, so will save a min or two for the next user if we correct this.

Related issues

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	Comments	Updated (UTC)
react-native-firebase	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 6, 2023 1:55pm
react-native-firebase-next	❌ Failed (Inspect)			Nov 6, 2023 1:55pm

[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]

Ooo - sorry about that! Thank you for the fix.
Looks like the CLA still needs signing before I can merge? You may follow the details link on that CI check and it will step you through it I believe

[mikehardy]

superceded by #7471