Fixed projects count in DORA performers score panel title

What does this MR do and why?

Fixes DORA performers score panel title to show the number of total projects with DORA metrics, rather than the total number of projects within the group.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Please make sure that you have a GitLab Ultimate license
2. Feature.enable(:dora_performers_score_panel, <group-id>)
3. Select a group with projects or seed a new group/project: SEED_DORA=1 FILTER=dora_metrics bundle exec rake db:seed_fu
4. Create a blank project under your chosen group to serve as the excluded project
5. Seed DoraPerformanceScoreCounts data for a project
6. Visit the Value streams dashboard for your chosen group (http://{YOUR_INSTANCE}/groups/{GROUP_PATH}/-/analytics/dashboards/value_streams_dashboard) and verify that panel title is correct

Seed Data

rails c

project = Project.find(<project-id>)
Dora::PerformanceScore.create(project: project, date: Time.current.last_month.beginning_of_month, deployment_frequency: 'high', lead_time_for_changes: 'high', time_to_restore_service: 'medium', change_failure_rate: 'high')

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #419490 (closed)