Fix contrast between background and form elements on some pages (#31266)

app/controllers/concerns/auth/two_factor_authentication_concern.rb

@@ -83,7 +83,6 @@ module Auth::TwoFactorAuthenticationConcern
   def prompt_for_two_factor(user)
     register_attempt_in_session(user)
 
-    @body_classes     = 'lighter'
     @webauthn_enabled = user.webauthn_enabled?
     @scheme_type      = if user.webauthn_enabled? && user_params[:otp_attempt].blank?
                           'webauthn'

app/controllers/concerns/challengable_concern.rb

@@ -42,7 +42,6 @@ module ChallengableConcern
   end
 
   def render_challenge
-    @body_classes = 'lighter'
     render 'auth/challenges/new', layout: 'auth'
   end