updated podfile to target v8 of the sdk

[StefanNedelchev]

Since iOS 14, apps are required to have Facebook SDK v8 (or later) for advertising campaigns to work. This PR updates the versions inside the Podfile. The app seems to build correctly after the change and login with Facebook seems to keep working too.

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Stefan Nedelchev.
This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email [email protected]
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails

[StefanNedelchev]

@cla-bot check

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Stefan Nedelchev.
This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email [email protected]
3. Make sure that the git commit email is configured in your GitHub account settings, see https://github.com/settings/emails

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!