Fix incorrect `page_title`, `nav`, and `header_title` usage in EE views

ee/app/views/groups/sso/saml.html.haml

-- page_title = _('SAML SSO for %{group_name}') % { group_name: @group_name }
+- page_title _('SAML SSO for %{group_name}') % { group_name: @group_name }
 
 = render 'devise/shared/tab_single', tab_title: _('SAML SSO')
 .login-box

ee/app/views/projects/prometheus/metrics/edit.html.haml

 - add_to_breadcrumbs _("Settings"), edit_project_path(@project)
 - add_to_breadcrumbs _("Integrations"), project_settings_integrations_path(@project)
 - add_to_breadcrumbs "Prometheus", edit_project_service_path(@project, PrometheusService)
-- breadcrumb_title = s_('Metrics|Edit metric')
+- breadcrumb_title s_('Metrics|Edit metric')
 - page_title @metric.title, s_('Metrics|Edit metric')
 = render 'form', project: @project, metric: @metric

ee/app/views/projects/prometheus/metrics/new.html.haml

 - add_to_breadcrumbs _("Settings"), edit_project_path(@project)
 - add_to_breadcrumbs _("Integrations"), project_settings_integrations_path(@project)
 - add_to_breadcrumbs "Prometheus", edit_project_service_path(@project, PrometheusService)
-- breadcrumb_title = s_('Metrics|New metric')
+- breadcrumb_title s_('Metrics|New metric')
 - page_title s_('Metrics|New metric')
 = render 'form', project: @project, metric: @metric