Fix tests to avoid new switch warnings

The tests changed in this commit now caused switch warnings (which
was correct). Remove the @switch annotation to avoid the warning.

Author: odersky

tests/pos/typers.scala

@@ -77,7 +77,7 @@ object typers {
 
   class C {
 
-    @tailrec final def factorial(acc: Int, n: Int): Int = (n: @switch) match {
+    @tailrec final def factorial(acc: Int, n: Int): Int = n match {
       case 0 => acc
       case _ => factorial(acc * n, n - 1)
     }

tests/run/switches.scala

@@ -18,7 +18,7 @@ object Test extends App {
     case _ => 4
   }
 
-  val x3 = (x: @switch) match {
+  val x3 = x match {
     case '0' if x > 0 => 0
     case '1' => 1
     case '2' => 2

tests/run/t5830.scala

@@ -10,7 +10,7 @@ object Test extends dotty.runtime.LegacyApp {
     case 'c' =>
   }
 
-  def ifThenElse(ch: Char, eof: Boolean) = (ch: @switch) match {
+  def ifThenElse(ch: Char, eof: Boolean) = ch match {
     case 'a' if eof => println("a with oef") // then branch
     case 'a' if eof => println("a with oef2") // unreachable, but the analysis is not that sophisticated
     case 'a' => println("a") // else-branch
@@ -22,7 +22,7 @@ object Test extends dotty.runtime.LegacyApp {
     case _ => println("default")
   }
 
-  def defaults(ch: Char, eof: Boolean) = (ch: @switch) match {
+  def defaults(ch: Char, eof: Boolean) = ch match {
     case _ if eof => println("def with oef") // then branch
     case _ if eof => println("def with oef2") // unreachable, but the analysis is not that sophisticated
     case _ => println("def") // else-branch