Improve details_enabled site setting description copy (#12560)

Improve details_enabled site setting description copy (#12560)

The details_enabled site setting description did not clearly convey what it controls.

The copy change was discussed here:

diff --git a/plugins/discourse-details/config/locales/server.en.yml b/plugins/discourse-details/config/locales/server.en.yml
index 0e78331..a616075 100644
--- a/plugins/discourse-details/config/locales/server.en.yml
+++ b/plugins/discourse-details/config/locales/server.en.yml
@@ -1,5 +1,5 @@
-    details_enabled: 'Enable the details feature. If you change this, you must rebake all posts with: "rake posts:rebake".'
+    details_enabled: 'Include the ability to add expandable details to a post. This feature can be found in the toolbar popup menu of the composer. You must rebake all posts with "rake posts:rebake" if you change this setting.'
     excerpt_details: "(click for more details)"

GitHub sha: c672ee28

This commit appears in #12560 which was approved by markvanlan. It was merged by tshenry.