Merge pull request #1346 from scalacenter/fix-dead-links

Fix remaining dead links

Author: julienrf

blog/_posts/2017-10-16-fourth-dotty-milestone-release.md

@@ -18,7 +18,7 @@ You can learn more about Dotty on our [website](https://dotty.epfl.ch).
 
 <!--more-->
 
-This is our fourth scheduled release according to our [6-week release schedule](https://dotty.epfl.ch/docs/usage/version-numbers.html).
+This is our fourth scheduled release according to our 6-week release schedule.
 The [previous technology preview](/blog/2017/09/07/third-dotty-milestone-release.html) improved
 stability and reliability.
 

blog/_posts/2018-10-04-scaladoc-tables.md

@@ -97,7 +97,7 @@ For a smorgasbord of examples take a look at [examples](https://janekdb.github.i
 
 ### Dotty and Scala 3
 
-With `dotty` now boosting its share of the development horizon it's important to place GFM into a [dottydoc](https://dotty.epfl.ch/docs/usage/dottydoc.html) and hence Scaladoc 3 context.
+With `dotty` now boosting its share of the development horizon it's important to place GFM into a [dottydoc](https://docs.scala-lang.org/scala3/guides/scaladoc/) and hence Scaladoc 3 context.
 
 In overview `dottydoc` supports the current Scaladoc 2.12 MediaWiki flavored markdown, but it also supports more contemporary flavors of markdown.
 

community/index.md

@@ -141,7 +141,7 @@ items and opinions.  Ask your Scala friends who they follow on Twitter
 
 ## Community-Powered Learning Resources
 
-* [Scala Exercises](http://scala-exercises.47deg.com/)
+* [Scala Exercises](http://scala-exercises.org/)
 * [Scala School](https://twitter.github.io/scala_school/)
 * [Scala Puzzlers](https://scalapuzzlers.com/)
 * [Scala Cookbook](http://www.scalacookbook.com/)