Support Expo 48

[louiszawadzki]

What does this PR do?

Support Expo 48

Motivation

Expo 48 is in beta, will be released soon. It bumps the RN version to 0.71, which required a change in the config plugin that applies the custom task to the build.gradle.

Additional Notes

The change was tested on a brand new expo 48 app.

Review checklist (to be filled by reviewers)

• [x] Feature or bugfix MUST have appropriate tests
• [x] Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• [x] Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• [x] If this PR is auto-generated, please make sure also to manually update the code related to the change

[louiszawadzki]

Yes, I'm a bit reluctant to remove the escaping characters for regexes, I've seen regex fail because of these in unexpected ways. If this becomes more of a problem later, I'll look into what we can do.