Update lexxy to 0.9.5.beta (#2820)

* Update lexxy to 0.9.5.beta

* Fix syntax highlight controller for lexxy 0.9.5.beta

The highlightAll export was renamed to highlightCode.

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Co-authored-by: Mike Dalessio <mike@37signals.com>

app/javascript/controllers/syntax_highlight_controller.js

@@ -1,8 +1,8 @@
 import { Controller } from "@hotwired/stimulus"
-import { highlightAll } from "lexxy"
+import { highlightCode } from "lexxy"
 
 export default class extends Controller {
   connect() {
-    highlightAll()
+    highlightCode()
   }
 }