Update coroutines.md
Update coroutines.md

Description of real laziness of a sequence was a bit confusing -- simplifying terms to make it clearer
JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,meilalina/kotlin-web-site,hltj/kotlin-web-site-cn,meilalina/kotlin-web-site,madvirus/kotlin-web-site,meilalina/kotlin-web-site,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,meilalina/kotlin-web-site,madvirus/kotlin-web-site,madvirus/kotlin-web-site