refactor: remove dbplyr and dplyr integration

[JosiahParry]

Checklist

• [x] update NEWS.md
• [x] documentation updated with devtools::document()
• [] devtools::check() passes locally

Changes

This PR removes the dbplyr integration with arcgislayers.

Issues that this closes

Closes #218 #111 #224

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CC @elipousson will this affect you at all?

[elipousson]

I'm good – never got accustomed to using this feature so no problems with seeing it go away.