Replace local vars with `let` in JS-enabled system specs (#34905)

spec/system/account_notes_spec.rb

@@ -11,13 +11,13 @@ RSpec.describe 'Account notes', :inline_jobs, :js, :streaming do
   let(:finished_onboarding) { true }
 
   let!(:other_account) { Fabricate(:account) }
+  let(:note_text) { 'This is a personal note' }
 
   before { as_a_logged_in_user }
 
   it 'can be written and viewed' do
     visit_profile(other_account)
 
-    note_text = 'This is a personal note'
     fill_in frontend_translations('account_note.placeholder'), with: note_text
 
     # This is a bit awkward since there is no button to save the change

spec/system/new_statuses_spec.rb

@@ -9,12 +9,12 @@ RSpec.describe 'NewStatuses', :inline_jobs, :js, :streaming do
   let(:password)            { 'password' }
   let(:confirmed_at)        { Time.zone.now }
   let(:finished_onboarding) { true }
+  let(:status_text) { 'This is a new status!' }
 
   before { as_a_logged_in_user }
 
   it 'can be posted' do
     visit_homepage
-    status_text = 'This is a new status!'
 
     within('.compose-form') do
       fill_in frontend_translations('compose_form.placeholder'), with: status_text