fix proxies config base on docker documents (#15766)

## DESCRIBE YOUR PR
fix proxies config base on [docker
document](https://docs.docker.com/engine/cli/proxy/)

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Signed-off-by: Hoai-Thu Vuong <thuvh87@gmail.com>

Author: thuvh

develop-docs/self-hosted/index.mdx

@@ -139,9 +139,11 @@ By default Sentry sends anonymous usage statistics to the Sentry team. It helps
 ```json
 {
   "proxies": {
-    "httpProxy": "http://proxy:3128",
-    "httpsProxy": "http://proxy:3128",
-    "noProxy": "smtp,memcached,redis,postgres,pgbouncer,kafka,clickhouse,seaweedfs,snuba-api,symbolicator,web,worker,nginx,relay,vroom,taskbroker,172.17.0.0/16,127.0.0.0/8"
+    "default": {
+      "httpProxy": "http://proxy:3128",
+      "httpsProxy": "http://proxy:3128",
+      "noProxy": "smtp,memcached,redis,postgres,pgbouncer,kafka,clickhouse,seaweedfs,snuba-api,symbolicator,web,worker,nginx,relay,vroom,taskbroker,172.17.0.0/16,127.0.0.0/8"
+    }
   }
 }
 ```