doc(step-by-step): readability improvements (#820)

This diff contains readability improvements for the step-by-step design document.

Co-authored-by: Simone Basso <bassosimone@gmail.com>

internal/model/README.md

@@ -1,4 +1,4 @@
-# Package github.com/ooni/probe-engine/model
+# Package github.com/ooni/probe-cli/internal/model
 
 Shared data structures and interfaces. We include in this
 package the most fundamental types. Use `go doc` to get

internal/model/measurement.go

@@ -57,7 +57,7 @@ type Measurement struct {
 
 	// MeasurementStartTimeSaved is the moment in time when we
 	// started the measurement. This is not included into the JSON
-	// and is only used within probe-engine as a "zero" time.
+	// and is only used within the ./internal pkg as a "zero" time.
 	MeasurementStartTimeSaved time.Time `json:"-"`
 
 	// Options contains command line options