minor #16464 Fix Markdown code syntax instead of RST (jmsche)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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Fix Markdown code syntax instead of RST

Commits
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50b6978 Fix Markdown code syntax instead of RST

Author: javiereguiluz

frontend/encore/installation.rst

@@ -188,12 +188,12 @@ a system that you'll learn about soon:
 And finally, create an ``assets/controllers.json`` file, which also fits into
 the Stimulus system:
 
-```json
-{
-    "controllers": [],
-    "entrypoints": []
-}
-```
+.. code-block:: json
+
+    {
+        "controllers": [],
+        "entrypoints": []
+    }
 
 You'll customize and learn more about these files in :doc:`/frontend/encore/simple-example`.
 When you execute Encore, it will ask you to install a few more dependencies based