update the command usage for `runc start`
update the command usage for `runc start`

The patch mainly removes the wrong "for writing".
The config files are readonly when `runc start`.

Signed-off-by: Lai Jiangshan <b337eedf453972390e4695e362aeea2634ef4e0c@gmail.com>

opencontainers/runc,keloyang/runc,nkwilson/runc,InformatiQ/runc,maxamillion/runc,docker/runc,inatatsu/runc,rhatdan/runc,hqhq/runc,kolyshkin/runc,zenlinTechnofreak/runc,coolljt0725/runc,docker/runc,liuwharton/runc,sunyuan3/runc,jhowardmsft/runc,sunyuan3/runc,mheon/runc,dqminh/runc,estesp/runc,chenchun/runc,docker/runc,avagin/runc,justincormack/runc,avagin/runc,stefanberger/runc,stefanberger/runc,sallyom/runc,maxamillion/runc,HardikDR/runc,mheon/runc,mheon/runc,laijs/runc,keloyang/runc,mYmNeo/runc,WeiZhang555/runc,keloyang/runc,dqminh/runc,hqhq/runc,wangkirin/runc,opencontainers/runc,xiaochenshen/runc,nkwilson/runc,YujiOshima/runc,runcom/runc,InformatiQ/runc,WeiZhang555/runc,vbatts/runc,abduld/runc,stefanberger/runc,liuwharton/runc,YujiOshima/runc,coolljt0725/runc,vbatts/runc,HardikDR/runc,jhowardmsft/runc,wking/runc,shishir-a412ed/runc,adrianreber/runc,sallyom/runc,kimh/runc,marcosnils/runc,sunyuan3/runc,crosbymichael/runc,inatatsu/runc,cyphar/runc,mikebrow/runc,vbatts/runc,kimh/runc,adrianreber/runc,rhatdan/runc,avagin/runc,dqminh/runc,albertoleal/runc,abduld/runc,justincormack/runc,marcosnils/runc,mikebrow/runc,zenlinTechnofreak/runc,shishir-a412ed/runc,rajasec/runc,runcom/runc,WeiZhang555/runc,ZJU-SEL/runc,ZJU-SEL/runc,hqhq/runc,nkwilson/runc,opencontainers/runc,justincormack/runc,mYmNeo/runc,shishir-a412ed/runc,wking/runc,jhowardmsft/runc,zenlinTechnofreak/runc,estesp/runc,liuwharton/runc,crosbymichael/runc,chenchun/runc,InformatiQ/runc,ZJU-SEL/runc,fabiokung/runc,wcwxyz/runc,gitido/runc,kimh/runc,runcom/runc,fabiokung/runc,inatatsu/runc,cloudfoundry-incubator/runc,sallyom/runc,YujiOshima/runc,rhatdan/runc,kolyshkin/runc,rajasec/runc,wking/runc,xiaochenshen/runc,cyphar/runc,mikebrow/runc,cloudfoundry-incubator/runc,estesp/runc,cyphar/runc,gitido/runc,wangkirin/runc,albertoleal/runc,laijs/runc,marcosnils/runc,wangkirin/runc,HardikDR/runc,abduld/runc,wcwxyz/runc,kolyshkin/runc,kolyshkin/runc,maxamillion/runc,opencontainers/runc,mYmNeo/runc,dqminh/runc,chenchun/runc,cloudfoundry-incubator/runc,adrianreber/runc,coolljt0725/runc,wcwxyz/runc,albertoleal/runc,laijs/runc,crosbymichael/runc,fabiokung/runc,gitido/runc,rajasec/runc,rhatdan/runc,xiaochenshen/runc