Remove file copy from www (#25429)

Author: tesseralis

docs/blog/2017-02-21-1-0-progress-update-where-came-from-where-going/gatsbygram.mp4 docs/blog/gatsbygram-case-study/gatsbygram.mp4

@@ -16,7 +16,7 @@ playing with the code!
 
 <div>
   <video controls="controls" autoplay="true" loop="true">
-    <source type="video/mp4" src="/gatsbygram.mp4" />
+    <source type="video/mp4" src="gatsbygram.mp4" />
     <p>Your browser does not support the video element.</p>
   </video>
 </div>

docs/blog/gatsbygram-case-study/index.md

@@ -1,5 +1,4 @@
 const Promise = require(`bluebird`)
-const fs = require(`fs-extra`)
 const startersRedirects = require(`./starter-redirects.json`)
 
 const { loadYaml } = require(`./src/utils/load-yaml`)
@@ -124,10 +123,3 @@ exports.createPages = async helpers => {
     })
   })
 }
-
-exports.onPostBuild = () => {
-  fs.copySync(
-    `../docs/blog/2017-02-21-1-0-progress-update-where-came-from-where-going/gatsbygram.mp4`,
-    `./public/gatsbygram.mp4`
-  )
-}