[Swift] Remove swift folder from this repository

[raulcd]

Describe the enhancement requested

The swift implementation has been moved to https://github.com/apache/arrow-swift and we can remove the swift/ subfolder now. No integration tests are being run for swift so we can do it now.

Component(s)

Swift

[kou]

Issue resolved by pull request 46804
#46804