Don't add aditional labels to GH runner

For now, the aditional labels would only contain the job ID that triggered
the creation of the runner. It does not make sense to add this label to the
actual runner that registeres against github. We can simply use it internally
by fetching it from the DB.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

runner/pool/pool.go

@@ -743,10 +743,6 @@ func (r *basePoolManager) addInstanceToProvider(instance params.Instance) error
 	labels = append(labels, r.controllerLabel())
 	labels = append(labels, r.poolLabel(pool.ID))
 
-	if len(instance.AditionalLabels) > 0 {
-		labels = append(labels, instance.AditionalLabels...)
-	}
-
 	jwtValidity := pool.RunnerTimeout()
 
 	entity := r.helper.String()