some builtin bridges seem to be down

Investigate if all builtin bridges are reachable and update the list if needed.

tasks:

• investigate why 91A6354697E6B02A386312F68D82CF86824D3606 and 011F2599C0E9B27EE74B353155E244813763C3E5 are giving errors in bridgestrap
• remove CDF2E852BF539B82BD10E27E9115A31734E378C2 from the builtin bridges
• consider if we need more builtin bridges
• moat could only distribute functional builtin bridges
• bring back an alert for bridges been down