Document mistake - filter to use fix #3712

Author: jknack

docs/asciidoc/routing.adoc

@@ -467,7 +467,7 @@ interface Filter {
 ----
 {
   /** Kotlin uses implicit variables: `ctx` and `next` */
-  filter {
+  use {
     val start = System.currentTimeMillis()  // <1>
 
     val response = next.apply(ctx)          // <2>
@@ -1014,14 +1014,14 @@ A `scoped filter` looks like:
 ----
 {
   // Increment +1
-  filter {
+  use {
     val n = next.apply(ctx) as Int
     return 1 + n
   }
 
   routes {                                // <1>
     // Multiply by 2
-    filter {
+    use {
       val n = next.apply(ctx) as Int
       2 * n
     }