docs(remote-config)!: update docs to be explicit about new behavior

[mikehardy]

A commit just to get a breaking change notice in the commit log for auto-population on semantic release.

Related #4157

BREAKING CHANGE:

    fetchAndActivate
        Previous behaviour returned a boolean indicating if config values were activated
        New behaviour returns a boolean indicating if any config values were fetched remotely.

    activate
        Previous behaviour returned a boolean indicating if config values were activated
        New behaviour returns a boolean indicating if any local config values were activated.

Description

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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