Update MiMaFilters and error code snippets

Author: odersky

docs/_docs/reference/error-codes/E164.md

@@ -39,8 +39,8 @@ class Derived extends Base {
   |   => String
   | but none of the attempts shown below succeeded:
   |
-  |   ==> => Int  <:  => String
-  |     ==> Int  <:  String  = false
+  |   ==> => Int  <:  => String in frozen constraint
+  |     ==> Int  <:  String in frozen constraint = false
   |
   | The tests were made under the empty constraint
    -----------------------------------------------------------------------------

project/MiMaFilters.scala

@@ -17,6 +17,11 @@ object MiMaFilters {
         ProblemFilters.exclude[DirectMissingMethodProblem]("scala.collection.generic.IsSeq.iarrayIsSeq"),
         // new annotation encoding capture checking's `x.except[C]` capabilities
         ProblemFilters.exclude[MissingClassProblem]("scala.annotation.internal.exceptCapability"),
+
+        ProblemFilters.exclude[MissingClassProblem]("scala.magic.package"),
+        ProblemFilters.exclude[MissingClassProblem]("scala.magic.package$"),
+        ProblemFilters.exclude[MissingClassProblem]("scala.magic.compiletime.package"),
+        ProblemFilters.exclude[MissingClassProblem]("scala.magic.compiletime.package$"),
     ))
 
     val BackwardsBreakingChanges: Map[String, Seq[ProblemFilter]] = Map(