Correct sentence (home-assistant#4302)

delneet · fabaff · commit 899331a6c6d1 · 2017-12-29T22:47:51.000+01:00
The sentence was missing the word _inside_.
diff --git a/source/_components/notify.slack.markdown b/source/_components/notify.slack.markdown
@@ -42,7 +42,7 @@ Configuration variables:
 
 ### {% linkable_title Slack service data %}
 
-The following attributes can be placed `data` for extended functionality.
+The following attributes can be placed inside `data` for extended functionality.
 
 | Service data attribute | Optional | Description |
 | ---------------------- | -------- | ----------- |
