Format AGENTS.md

Author: sij411

AGENTS.md

@@ -350,12 +350,12 @@ See *CONTRIBUTING.md* for complete Markdown conventions.
 
 
 Issues and PR descriptions
---------------------
+--------------------------
 
  -  Unlike other Markdown files in this repository, do not wrap lines at
     80 columns
  -  Follow the documentation standards and Markdown conventions sections above
     for all other formatting
  -  Use `#123` shorthand for issue and PR references instead of permalink URLs
  -  Include rationales in descriptions: explain the background and motivation
-    behind the change, not just what was changed
+    behind the change, not just what was changed