[gitlab-org/gitlab] Update subheader copy on Trial registration first page

### ROOT CAUSE The current subheader copy on the trial registration page doesn't explicitly state that no credit card is required, leading to user concerns about being charged after the trial period. ### CODE FIX To update the subheader copy, modify the relevant file:

erb
# app/views/trial_registrations/new.html.erb

<% partial :sub_header do %>
  <%= h("Start your free 30 day trial today, **no credit card required**. You'll have full access to our most advanced features, including GitLab Duo Agent Platform") %>
<% end %>


This change ensures users are clearly informed that no credit card is needed during the trial period.