docs(generic): update genericShow module reference

[sevillaarvin]

I tried executing the code found in the Generic section but kept getting an error:

Data.Generic.Rep.Show

#+begin_src purescript
import Data.Generic.Rep (class Generic)
-- import Data.Show.Generic (genericShow)
import Data.Generic.Rep.Show (genericShow)
import Effect.Console (logShow)

newtype Score = Score Int

:paste

-- generic deriving prints wrapper with show
derive instance genericScore :: Generic Score _
instance showScore :: Show Score where
  show = genericShow

main = logShow (Score 5)
-- Prints:
-- (Score 5)
#+end_src

#+RESULTS:
#+begin_example
PSCi, version 0.14.0
Type :? for help

import Prelude

> > > Error found:
in module �[33m$PSCI�[0m
at <internal>:0:0 - 0:0 (line 0, column 0 - line 0, column 0)

  Unknown module �[33mData.Generic.Rep.Show�[0m


See https://github.com/purescript/documentation/blob/master/errors/UnknownName.md for more information,
or to contribute content related to this error.


> > > > > … … … … … … … … … … Error found:
in module �[33m$PSCI�[0m
at :5:10 - 5:21 (line 5, column 10 - line 5, column 21)

  Unknown value �[33mgenericShow�[0m


See https://github.com/purescript/documentation/blob/master/errors/UnknownName.md for more information,
or to contribute content related to this error.


> See ya!
()
#+end_example

Per Data.Generic.Rep.Show in pursuit, the package is deprecated.

I looked for the genericShow function and found it in Data.Show.Generic:

Data.Show.Generic

#+begin_src purescript
import Data.Generic.Rep (class Generic)
import Data.Show.Generic (genericShow)
-- import Data.Generic.Rep.Show (genericShow)
import Effect.Console (logShow)

newtype Score = Score Int

:paste

-- generic deriving prints wrapper with show
derive instance genericScore :: Generic Score _
instance showScore :: Show Score where
  show = genericShow

main = logShow (Score 5)
-- Prints:
-- (Score 5)
#+end_src

#+RESULTS:
: PSCi, version 0.14.0
: Type :? for help
: 
: import Prelude
: 
: > > > > > > > > … … … … … … … … … … > See ya!
: ()