Google Cloud Monitoring: Fix project variable (#66524)

Google Cloud Monitoring: fix project variable

Also fix typo found while debugging

pkg/tsdb/cloudmonitoring/cloudmonitoring.go

@@ -645,7 +645,7 @@ func (s *Service) getDSInfo(pluginCtx backend.PluginContext) (*datasourceInfo, e
 
 	instance, ok := i.(*datasourceInfo)
 	if !ok {
-		return nil, fmt.Errorf("failed to cast datsource info")
+		return nil, fmt.Errorf("failed to cast datasource info")
 	}
 
 	return instance, nil