Remove terminal.Writer

terminal.Writer is now just a wrapper around stdio.Stdout() without
any useful functionality.  Replace it with stdio.Stdout() as an
io.Writer.

Test: ui/terminal/status_test.go
Change-Id: I5bc5476afdca950b505642f0135a3af9d37fbe24

ui/terminal/dumb_status.go

@@ -16,19 +16,20 @@ package terminal
 
 import (
 	"fmt"
+	"io"
 
 	"android/soong/ui/status"
 )
 
 type dumbStatusOutput struct {
-	writer    Writer
+	writer    io.Writer
 	formatter formatter
 }
 
 // NewDumbStatusOutput returns a StatusOutput that represents the
 // current build status similarly to Ninja's built-in terminal
 // output.
-func NewDumbStatusOutput(w Writer, formatter formatter) status.StatusOutput {
+func NewDumbStatusOutput(w io.Writer, formatter formatter) status.StatusOutput {
 	return &dumbStatusOutput{
 		writer:    w,
 		formatter: formatter,