fix: test data api route used old name for test data datasource, fixes #12773

pkg/api/metrics.go

@@ -99,7 +99,7 @@ func GetTestDataRandomWalk(c *m.ReqContext) Response {
 	timeRange := tsdb.NewTimeRange(from, to)
 	request := &tsdb.TsdbQuery{TimeRange: timeRange}
 
-	dsInfo := &m.DataSource{Type: "grafana-testdata-datasource"}
+	dsInfo := &m.DataSource{Type: "testdata"}
 	request.Queries = append(request.Queries, &tsdb.Query{
 		RefId:      "A",
 		IntervalMs: intervalMs,