Change documentation link protocol from http to https.
Change documentation link protocol from http to https.

Riccorl/kotlin-koans,Kotlin/kotlin-koans,Carighan/kotlin-koans,TheCoinTosser/Kotlin-Koans---Solutions,JetBrains/workshop-jb,Riccorl/kotlin-koans,enchf/kotlin-koans,trmollet/tuto_kotlin,hughandrewarch/kotlin-koans,hughandrewarch/kotlin-koans,TheCoinTosser/Kotlin-Koans---Solutions,zyallday/kotlin-koans,Carighan/kotlin-koans,Kotlin/kotlin-koans,enchf/kotlin-koans,trmollet/tuto_kotlin,zyallday/kotlin-koans,JetBrains/workshop-jb