[fix] KOSync plugin server location (#3288)

This is only step one. It remains to be determined why the connection is downgraded to sslv3, which will result in a handshake failure.

plugins/kosync.koplugin/api.json

@@ -1,5 +1,5 @@
 {
-    "base_url" : "https://vislab.bjmu.edu.cn:7200/",
+    "base_url" : "https://sync.koreader.rocks:443/",
     "name" : "koreader-sync-api",
     "methods" : {
         "register" : {

spec/unit/kosync_spec.lua

@@ -1,6 +1,6 @@
 local service = [[
 {
-    "base_url" : "https://vislab.bjmu.edu.cn:7200",
+    "base_url" : "https://sync.koreader.rocks:443/",
     "name" : "api",
     "methods" : {
         "register" : {