chore: do not log context timeouts from traversal workers

[zinic]

Description

In a parallel BFS traversal, it's possible that some workers are unable to start due to connection slots being unavailable. This can result in a situation where the traversal naturally finishes but because workers are locked into waiting for a connection slot, they surface the context cancellation as a failure.

Motivation and Context

Log noise and better behaved traversal.

Types of changes

• Chore (a change that does not modify the application functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Documentation updates are needed, and have been made accordingly.
• I have added and/or updated tests to cover my changes.
• All new and existing tests passed.
• My changes include a database migration.

[rvazarkar]

lgtm