chore(update): updated step title

refs #1784 (comment)

- as per feedback in referenced link

lib/commands/update.js

@@ -94,7 +94,7 @@ class UpdateCommand extends Command {
             title: 'Linking latest Ghost and recording versions',
             task: this.link
         }, {
-            title: 'Installing default themes',
+            title: 'Linking built-in themes',
             task: this.linkDefaultThemes
         }, {
             title: 'Running database migrations',
@@ -243,7 +243,7 @@ class UpdateCommand extends Command {
                     }
                 }
             }
-        } 
+        }
 
         // ensure all default themes (e.g. themes shipped with Ghost) are symlinked to /content/themes directory
         if (fs.existsSync(currentThemesDir)) {