修复nginx.conf错误 (#776)

Fix nginx: [emerg] unknown directive.
Log
`nginx: [emerg] unknown directive "client_body_buffer_size:" in /etc/nginx/nginx.conf:18
`

docker/nginx.conf

@@ -15,7 +15,7 @@ http {
 	server_tokens off;
 
 	client_max_body_size 20m;
-	client_body_buffer_size: 20m;
+	client_body_buffer_size 20m;
 
 	keepalive_timeout 65;
 
@@ -42,4 +42,4 @@ http {
 
 	access_log /var/log/nginx/access.log main;
 	include /etc/nginx/conf.d/*.conf;
-}
+}