Stop the deprecation of Data.Monoid.{First,Last}

[Henning Thielemann]

On Sat, 11 Apr 2020, Simon Jakobi via Libraries wrote:

> For two years there has been a plan ([1], [12]) to deprecate and
> eventually remove Data.Monoid.{First,Last} ([13]), in order to resolve
> the name conflict with Data.Semigroup.{First,Last} ([14]).

I find it sad, that in 2020 we still discuss removing things because of 
name clashes. In order to conform to the PVP we should import explicitly 
or with qualification anyway. If users depend on the Maybe-First in Monoid 
then I am happy with maintaining both Semigroup.First and Monoid.First.