Fix Latest timestamp metric to return timestamp in seconds

[alecgard]

• Made a rookie mistake when first adding this metric and extracted the Seconds component of the time, rather than the time in seconds 🤦.

[alecgard]

Build External Repositories > Build Chainlink Image workflow is failing, but this should be unrelated and appears to have been failing for a while: https://github.com/smartcontractkit/chainlink-common/actions/workflows/build_external.yml

Failing due to:

go: github.com/smartcontractkit/chainlink/v2/core/services/chainlink imports
	github.com/smartcontractkit/chainlink-common/pkg/loop/adapters/relay: module 
github.com/smartcontractkit/chainlink-common@latest found (v0.3.0), but does not contain package 
github.com/smartcontractkit/chainlink-common/pkg/loop/adapters/relay