replace unicode arrows

* ⇒, →, ←
* because we don't want to show them in documentation snippets and
  then it's complicated to avoid that when snippets are
  located in src/test/scala in individual modules
* dont replace object `→` in FSM.scala and PersistentFSM.scala

akka-stream/src/main/scala/akka/stream/impl/JsonObjectParser.scala

@@ -29,11 +29,11 @@ import scala.annotation.switch
   final val Space = 32 // ' '
 
   def isWhitespace(b: Byte): Boolean = (b: @switch) match {
-    case Space      ⇒ true
-    case LineBreak  ⇒ true
-    case LineBreak2 ⇒ true
-    case Tab        ⇒ true
-    case _          ⇒ false
+    case Space      => true
+    case LineBreak  => true
+    case LineBreak2 => true
+    case Tab        => true
+    case _          => false
   }
 
 }
@@ -79,8 +79,8 @@ import scala.annotation.switch
     if (!foundObject) None
     else
       (pos: @switch) match {
-        case -1 | 0 ⇒ None
-        case _ ⇒
+        case -1 | 0 => None
+        case _ =>
           val (emit, buf) = buffer.splitAt(pos)
           buffer = buf.compact
           pos = 0