[tor-relays] Please update standalone snowflake proxy to v2.13.1

Hello, After receiving reports of Snowflake proxies being blocked by DTLS fingerprint in Russia[0], we updated the standalone proxy to enable a new DTLS randomization and mimicry feature[1] by default. Proxy operators that are using the standalone version of the proxy will need to update or set the following command-line option: -covertdtls-config randomizemimic Browser-based proxies such as the browser badge or webextension were not blocked and do not require an update. Thank you for running a Snowflake proxy! [0] https://github.com/net4people/bbs/issues/603 [1] https://www.petsymposium.org/foci/2025/foci-2025-0006.pdf