docs(toh5): update styles.css link (#2601)

Author: tiangolo

public/docs/ts/latest/tutorial/toh-pt5.jade

@@ -878,7 +878,7 @@ block css-files
 
 +makeExcerpt('styles.css (excerpt)', 'toh')
 
-- var styles_css = 'https://raw.githubusercontent.com/angular/angular.io/master/public/docs/_examples/styles.css'
+- var styles_css = 'https://raw.githubusercontent.com/angular/angular.io/master/public/docs/_examples/_boilerplate/styles.css'
 
 :marked
   Create the file <span ngio-ex>styles.css</span>, if it doesn't exist already.