Return fewer data points in v2 btcPriceList query

[jrbuhl93]

The mobile app's graph has difficulty processing the number of data points provided in the 1 year and to a lesser extent the 1 month query in apiv2. This could be handled client side by filtering out data points, but it makes more sense to return fewer server side so that the transmitted data is less.

[nicolasburtey]

linked to https://github.com/GaloyMoney/galoy/pull/662