Merge pull request #13845 from danicheg/readme-fix

Use `https` protocol in the link in `README.md`

Author: nicolasstucki

README.md

@@ -3,7 +3,7 @@ Dotty
 [![Dotty CI](https://github.com/lampepfl/dotty/workflows/Dotty/badge.svg?branch=master)](https://github.com/lampepfl/dotty/actions?query=branch%3Amaster)
 [![Join the chat at https://gitter.im/scala/scala](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/scala/scala?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-* [Homepage](http://dotty.epfl.ch)
+* [Homepage](https://dotty.epfl.ch)
 * [Documentation](https://dotty.epfl.ch/docs)
 
 Try it out