[DOC] Fix incorrect code example regarding @metadata (#194)

Co-authored-by: camAtGitHub <camAtGitHub@users.noreply.github.com>

Author: andsel

CHANGELOG.md

@@ -1,3 +1,6 @@
+## Unreleased
+  - [DOC] Fix incorrect pipeline code snippet
+  
 ## 6.2.5
   - Update log4j dependency to 2.17.0
 

docs/index.asciidoc

@@ -105,9 +105,9 @@ If an event is missing this metadata, it can be copied into place from the sourc
 [source,txt]
 -----
 filter {
-  if [@metadata][input][tcp][source] and not [host] {
+  if [@metadata][input][tcp][source] and ![host] {
     mutate {
-      copy {
+      copy => {
         "[@metadata][input][tcp][source][name]" => "[host][name]"
         "[@metadata][input][tcp][source][ip]"   => "[host][ip]"
       }