Bump Trix to ^1.2.0

Adds an attachment button to the Trix toolbar that improves overall file upload usability, especially on mobile devices where files can't be dragged / dropped.

References:
- https://github.com/basecamp/trix/releases/tag/1.2.0
- https://github.com/basecamp/trix/pull/619
- https://github.com/basecamp/trix/issues/582

actiontext/package.json

@@ -24,6 +24,6 @@
     "@rails/activestorage": "^6.0.0-alpha"
   },
   "peerDependencies": {
-    "trix": "^1.0.0"
+    "trix": "^1.2.0"
   }
 }