Change reverse Geocoding concurrency to comply with Nominatim terms of use

[vwvierhundertzwoelf]

Describe the bug
When i start reverse geocoding, BACKGROUND_PROCESSING_CONCURRENCY tasks will be active with geocoding in sidekiq.
But in the Nominatim user policy it is only allowed to use the api once per second (Ref: https://operations.osmfoundation.org/policies/nominatim/)
This is resulting in a tempban and a lot of failed jobs as well as too much workload.
The only efficient way to get geocoding completed is to limit the BACKGROUND_PROCESSING_CONCURRENCY to 1 and after the bulk geocoding of an import is successfully reverse geocoded increase the number again.

Version
0.15.8

To Reproduce
Steps to reproduce the behavior:

1. Start reverse Geocoding
2. Goto sidekiq
3. See a lot of ECONNREFUSED

Expected behavior
Perform only one request per second to Nominatim, when using the official server.

Screenshots

[Freika]

Done in https://github.com/Freika/dawarich/releases/tag/0.16.9