Update docs/blog/_posts/2020-04-28-24th-dotty-milestone-release.md

Co-Authored-By: Nicolas Stucki <[email protected]>

Author: anatoliykmetyuk

docs/blog/_posts/2020-04-28-24th-dotty-milestone-release.md

@@ -63,7 +63,7 @@ class B extends A:
   inline override def f(x: Int) = s"Bar $x"
 
 @main def Test =
-  val b = B()
+  val b: B = B()
   println(b.f(22))
   val a: A = b
   println(a.f(22))