Update Project to Xcode 11.4 and Swift 5.2

[lennet]

We need to update

• [ ] .swift-version
• [ ] Xcode reference in our CI Actions (Not sure if Github Actions already supports the new Xcode version though)
• [ ] manually update dependencies and run swift-format just in case something changed for 5.2

[fbernutz]

At the moment Xcode 11.3.1 is still the default. (see here: https://github.com/actions/virtual-environments/blob/master/images/macos/macos-10.15-Readme.md#xcode)

[fbernutz]

They've installed the release version of Xcode 11.4 on the machines, so I think we could start using Xcode 11.4, when we change this line to 11.4: https://github.com/criticalmaps/criticalmaps-ios/blob/master/.github/workflows/main.yml#L12