test_runner: use yellow from util/colors

Refs: nodejs#47791

Author: dmnsgn

lib/internal/test_runner/utils.js

@@ -22,7 +22,7 @@ const { createWriteStream } = require('fs');
 const { pathToFileURL } = require('internal/url');
 const { createDeferredPromise } = require('internal/util');
 const { getOptionValue } = require('internal/options');
-const { green, red, white } = require('internal/util/colors');
+const { green, yellow, red, white } = require('internal/util/colors');
 
 const {
   codes: {
@@ -36,7 +36,7 @@ const { compose } = require('stream');
 const coverageColors = {
   '__proto__': null,
   'high': green,
-  'medium': '\u001b[33m',
+  'medium': yellow,
   'low': red,
 };