regression: disable notifiee handler on ios devices

[dnlsilva]

Proposed changes

The notification handler overwrites the handler used by the app's notification library, as we don't use notifications from the notification lib on iOS devices, disabling it solves the deeplink problem when the app is in the background.

Issue(s)

How to test or reproduce

• click on a push with the app in the background

Screenshots

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

Jira: [https://rocketchat.atlassian.net/browse/CORE-203]