Copy edit Learn Basics section.

chrome/common/extensions/docs/templates/json/chrome_sidenav.json

 [
   {
     "title": "Devtools",
     "items": [
       {
         "title": "Learn Basics",
         "items": [
           {
             "title": "Overview",
             "href": "/devtools/index"
@@ skipping 675 matching lines @@
         ]
       },
       {
         "title": "Native Client",
         "items": [
           {
             "title": "Learn Basics",
             "href": "/native-client/overview",
             "items": [
               {
-                "title": "What Is Native Client?",
+                "title": "Technical Overview",
                 "href": "/native-client/overview"
               },
               {
                 "title": "NaCl and PNaCl",
                 "href": "/native-client/nacl-and-pnacl"
               }
             ]
           },
           {
             "title": "SDK",
@@ skipping 294 matching lines @@
                 "title": "Articles",
                 "href": "/webstore/articles"
               }
             ]
           }
         ]
       }
     ]
   }
 ]