Update project build settings to iOS14

[am-MongoDB]

Related Issue

Fixes #364

Checklist:

• [x] I have read the contributor's guide.
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• [x] I have tested the change to the best of my ability against the sandbox or a local build.

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• [ ] My change adds new text and requires a change to translations.

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[Sheeri]

@am-MongoDB feel free to squash and merge at your leisure!