Minor: fix api reference url in nav.yml.
Minor: fix api reference url in nav.yml.

hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,tsuijten/kotlin-web-site,tsuijten/kotlin-web-site,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,tsuijten/kotlin-web-site,tsuijten/kotlin-web-site,hltj/kotlin-web-site-cn