[split] util: Update example version in README to latest v6.12.1
[split] util: Update example version in README to latest v6.12.1

Signed-off-by: Evan Meagher <evm@twitter.com>

RB_ID=292599

stremlenye/util,mosesn/util,folone/util,Jiri-Kremser/util,wuqiangxjtu/util,RUNDSP/util,stremlenye/util,slackhappy/util,folone/util,folone/util,slackhappy/util,LitmusHealth/twitter-utils,edombowsky/util,Jiri-Kremser/util,tenghuihua/util,nkhuyu/util,nkhuyu/util,LitmusHealth/twitter-utils,twitter/util,nkhuyu/util,mosesn/util,BuoyantIO/twitter-util,slackhappy/util,hydro2k/util,hydro2k/util,mosesn/util,LitmusHealth/twitter-utils,cogitate/twitter-util-uuid,stremlenye/util,travisbrown/util,BuoyantIO/twitter-util,Jiri-Kremser/util,tenghuihua/util,edombowsky/util,hydro2k/util,tdyas/util,wuqiangxjtu/util,luciferous/util,tenghuihua/util,wuqiangxjtu/util,RUNDSP/util,slackhappy/util,twitter/util,edombowsky/util,cogitate/twitter-util-uuid,Jiri-Kremser/util,edombowsky/util,folone/util,travisbrown/util,BuoyantIO/twitter-util,LitmusHealth/twitter-utils,twitter/util,hydro2k/util,travisbrown/util,RUNDSP/util,luciferous/util,stremlenye/util,cogitate/twitter-util-uuid,nkhuyu/util,luciferous/util,RUNDSP/util,tenghuihua/util,wuqiangxjtu/util,tdyas/util,tdyas/util,BuoyantIO/twitter-util,luciferous/util,travisbrown/util,cogitate/twitter-util-uuid,tdyas/util