Fastcoding logo as png (#2343) (#1873)

Author: vuejs-jp-bot

themes/vue/_config.yml

@@ -96,7 +96,7 @@ gold_sponsors:
     img: devexpress.png
     name: DevExpress
   - url: 'https://fastcoding.jp/javascript/ '
-    img: fastcoding_inc.svg
+    img: fastcoding_inc.png
     name: FASTCODING Inc
   - url: 'https://usave.co.uk/utilities/broadband'
     img: usave.png