Bump reflex-platform

[alexfmpe]

Android build currently fails in nix CI with

Configuring reflex-dom-0.6.3.1...
CallStack (from HasCallStack):
  die', called at libraries/Cabal/Cabal/Distribution/Simple/Configure.hs:950:20 in Cabal-2.4.0.1:Distribution.Simple.Configure
  configureFinalizedPackage, called at libraries/Cabal/Cabal/Distribution/Simple/Configure.hs:460:12 in Cabal-2.4.0.1:Distribution.Simple.Configure
  configure, called at libraries/Cabal/Cabal/Distribution/Simple.hs:596:20 in Cabal-2.4.0.1:Distribution.Simple
  confHook, called at libraries/Cabal/Cabal/Distribution/Simple/UserHooks.hs:67:5 in Cabal-2.4.0.1:Distribution.Simple.UserHooks
  configureAction, called at libraries/Cabal/Cabal/Distribution/Simple.hs:178:19 in Cabal-2.4.0.1:Distribution.Simple
  defaultMainHelper, called at libraries/Cabal/Cabal/Distribution/Simple.hs:115:27 in Cabal-2.4.0.1:Distribution.Simple
  defaultMain, called at Setup.hs:2:8 in main:Main
Setup: Encountered missing dependencies:
android-activity ==0.2.*