Fix example

Author: nicolasstucki

content/binary-api.md

@@ -155,10 +155,10 @@ class C {
   private def b: Int = ...
   @binaryAPI protected def c: Int = ...
   protected def d: Int = ...
-  final def C$inline$a: Int = ... // generated by `@binaryAPIAccessor`
-  final def C$inline$b: Int = ... // warn: `b` should be annotated with `@binaryAPIAccessor` + migration code
-  final def C$inline$d: Int = ... // warn: `d` should be annotated with `@binaryAPI` + migration code
-  inline def foo: Int = C$inline$a + C$inline$b + c + C$inline$d
+  final def C$$inline$a: Int = ... // generated by `@binaryAPIAccessor`
+  final def C$$inline$b: Int = ... // warn: `b` should be annotated with `@binaryAPIAccessor` + migration code
+  final def C$$inline$d: Int = ... // warn: `d` should be annotated with `@binaryAPI` + migration code
+  inline def foo: Int = C$$inline$a + C$$inline$b + c + C$$inline$d
 }
 ~~~