Modernize (#7089)

Use
https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize
to update code to new style.

---------

Co-authored-by: Flc゛ <four_leaf_clover@foxmail.com>
Co-authored-by: Damien Mathieu <42@dmathieu.com>

metric/example_test.go

@@ -166,7 +166,7 @@ func ExampleMeter_gauge() {
 	go func() {
 		defer close(fanSpeedSubscription)
 
-		for idx := 0; idx < 5; idx++ {
+		for range 5 {
 			// Synchronous gauges are used when the measurement cycle is
 			// synchronous to an external change.
 			// Simulate that external cycle here.