unset region per user request

src/langs/en.json

@@ -163,7 +163,7 @@
   "settings_s3_prod3": "Configuring CORS",
   "settings_s3_endpoint": "Endpoint",
   "settings_s3_region": "Region",
-  "settings_s3_region_desc": "If you are not sure what to enter, you could try the value: us-east-1",
+  "settings_s3_region_desc": "If you are not sure what to enter, you could try the value: us-east-1 . If you leave it empty, the client will try to ignore this setting.",
   "settings_s3_accesskeyid": "Access Key ID",
   "settings_s3_accesskeyid_desc": "Access key ID. Attention: Access key ID and other info are saved locally.",
   "settings_s3_secretaccesskey": "Secret Access Key",

src/langs/zh_cn.json

@@ -163,7 +163,7 @@
   "settings_s3_prod3": "设置 CORS",
   "settings_s3_endpoint": "服务地址（Endpoint）",
   "settings_s3_region": "区域（Region）",
-  "settings_s3_region_desc": "如果您不知道这个值填什么，可以尝试填写此默认值：us-east-1",
+  "settings_s3_region_desc": "如果您不知道这个值填什么，可以尝试填写：us-east-1。如果您不填写，客户端会尝试不设置此选项。",
   "settings_s3_accesskeyid": "Access Key ID",
   "settings_s3_accesskeyid_desc": "Access key ID。注意：access key ID 和其它信息都会在本地保存。",
   "settings_s3_secretaccesskey": "Secret Access Key",

src/langs/zh_tw.json

@@ -163,7 +163,7 @@
   "settings_s3_prod3": "設定 CORS",
   "settings_s3_endpoint": "服務地址（Endpoint）",
   "settings_s3_region": "區域（Region）",
-  "settings_s3_region_desc": "如果您不知道這個值填什麼，可以嘗試填寫此預設值：us-east-1",
+  "settings_s3_region_desc": "如果您不知道這個值填什麼，可以嘗試填寫：us-east-1。如果您不填寫，客戶端會嘗試不設定此選項。",
   "settings_s3_accesskeyid": "Access Key ID",
   "settings_s3_accesskeyid_desc": "Access key ID。注意：access key ID 和其它資訊都會在本地儲存。",
   "settings_s3_secretaccesskey": "Secret Access Key",