[backport] fix(webconnectivitylte): avoid data race

This diff backports 297360d.

Closes ooni/probe#2434

internal/experiment/webconnectivitylte/iox.go

@@ -33,8 +33,10 @@ func StreamAllContext(ctx context.Context, reader io.Reader) ([]byte, error) {
 	defer cancel()
 
 	go func() {
-		buffer := make([]byte, 1<<13)
 		for {
+			// Implementation note: the buffer MUST be created at each
+			// loop, otherwise we're data-racing with the reader.
+			buffer := make([]byte, 1<<13)
 			count, err := reader.Read(buffer)
 			if count > 0 {
 				data := buffer[:count]

internal/experiment/webconnectivitylte/measurer.go

@@ -37,7 +37,7 @@ func (m *Measurer) ExperimentName() string {
 
 // ExperimentVersion implements model.ExperimentMeasurer.
 func (m *Measurer) ExperimentVersion() string {
-	return "0.5.22"
+	return "0.5.23"
 }
 
 // Run implements model.ExperimentMeasurer.