github: Don't capture pointer in collector

Created by: ryanslade

We're seeing metrics being collected with names of non site owned external services, this should not be the case as we only set up collectors for site owned external services. The only way the wrong name could be coming through is if the pointer to the service that is captured by the collector closure is changed at some point. It's not clear where this could happen, but by passing the name through as a value we avoid this possibility.

The affected dashboard is here

Test plan

Deploy and check dashboard again