Workaround: Update dead link from temporarily inactive blog to 立川's Doorkeeper page

cf. coderdojo-japan/dojopaas#262

Author: yasulab

db/dojos.yml

@@ -1437,7 +1437,7 @@
   created_at: '2017-11-18'
   name: 立川
   prefecture_id: 13
-  url: https://coderdojotachikawa.github.io/
+  url: https://coderdojotachikawa.doorkeeper.jp/
   logo: "/img/dojos/tachikawa.webp"
   description: 立川市で毎月開催
   tags: