fix typo in slack task example

Author: brig

examples/slack/concord.yml

@@ -5,12 +5,12 @@ flows:
       channelId: "C5W9ELY7Q"
       text: "Process ${txId} is completed"
       username: "my bot"
-      icon_emoji: ":chart_with_upwards_trend:"
+      iconEmoji: ":chart_with_upwards_trend:"
       attachments:
         - fallback: "Book your flights at https://flights.example.com/book/r123456"
           actions:
             - type: "button"
               text: "Book flights"
               url: "https://flights.example.com/book/r123456"
 
-  - log: notified
+  - log: notified