[ios][camera] Fix path where camera saves picture on simulator

[pettomartino]

Why

When taking photo using takePictureAsync there is a specific implementation for the simulator.
However when building the directory where the file will be save, there is a small bug with the concatenation. The concatenation with the cacheDirectory is missing the slash (/) so it creates a folder called CachesCamera rather than Caches/Camera as the device implementation does.
This creates an issue because FileSystem can't access this folder thus files can't be deleted. This issue creates in inconsistency between development environment and real device.

How

I added a slash / to the string. Assuming this implementation works only on simulator which works only on macOS, the file system will always use / as directory separator so I believe we can just add this missing /

Test Plan

Use expo-camera and call the method takePictureAsync. Check the uri of the file generated.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).

[lukmccall]

Looks good to me 🔥
Thanks for your contribution 🏅