Improve SwiftLint config
Improve SwiftLint config

Removes unrecognized rule (`unused_private_declaration`) and analyzer rule in wrong place (`unused_import`). The analyzer rule may be reintroduced in the right place at a later date.

Esri/arcgis-runtime-samples-ios,Esri/arcgis-runtime-samples-ios,Esri/arcgis-runtime-samples-ios,Esri/arcgis-runtime-samples-ios