Deploy new tracker version

[josecelano]

PRs:

• Overhaul stats: Add new metric to the metrics endpoint with the current number of banned IPs torrust-tracker#1572
• Increase broadcaster channel capacity to 65536 torrust-tracker#1573
• Overhaul stats: Fix Prometheus export to include only one HELP and TYPE lines per metric torrust-tracker#1574
• Update dependencies torrust-tracker#1576

[josecelano]

Grafana dashboard and droplet graphs before deployment:

[josecelano]

Grafana dashboard (stats) after deployment: