mirrors: remove mirror.ufro.cl

according to https://mirror.ufro.cl/ our mirror was removed

Author: lazka

web/dev/mirrors.md

@@ -62,7 +62,6 @@ support (\*), HTTPS support, synced at least once per day from the primary serve
 | mirrors.aliyun.com | [HTTPS](https://mirrors.aliyun.com/msys2/) | <ali-yum@alibaba-inc.com> |
 | mirror.iscas.ac.cn | [HTTPS](https://mirror.iscas.ac.cn/msys2/) | |
 | mirrors.cloud.tencent.com | [HTTPS](https://mirrors.cloud.tencent.com/msys2/) | <petzhou@tencent.com> |
-| mirror.ufro.cl | [HTTPS](https://mirror.ufro.cl/msys2/) | [Jonathan Gutiérrez](mailto:jonathan.gutierrez@ufrontera.cl) |
 | download.nus.edu.sg | [HTTPS](https://download.nus.edu.sg/mirror/msys2/) | <download@nus.edu.sg> |
 
 ## Adding a New Mirror