iOS Guide: authenticationKeyPath needs a absolute path

[GitToTheHub]

Platforms affected

iOS

Motivation and Context

The documentation was unclear if an absolute path is needed for authenticationKeyPath . When using a relative path, the archiving will fail.

Description

Testing

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary