[PresentationUtil] Fix Canvas expression autocomplete (#146425)

Fixes #146243 

## Summary

Fixes Canvas expression autocomplete

#143739 upgraded the monaco-editor
dependency which uses a callback to the `onLanguage` method to
initialize the expressions. The PR moved the `monaco.languages.register`
command inside this callback and which was never triggered.

Moving the `monaco.languages.register` command outside the callback
appears to fix the issue.

src/plugins/presentation_util/public/components/expression_input/language.ts

@@ -116,7 +116,7 @@ export function registerExpressionsLanguage(functions: ExpressionFunction[]) {
   expressionsLanguage.keywords = functions.map((fn) => fn.name);
   expressionsLanguage.deprecated = functions.filter((fn) => fn.deprecated).map((fn) => fn.name);
   monaco.languages.onLanguage(EXPRESSIONS_LANGUAGE_ID, () => {
-    monaco.languages.register({ id: EXPRESSIONS_LANGUAGE_ID });
     monaco.languages.setMonarchTokensProvider(EXPRESSIONS_LANGUAGE_ID, expressionsLanguage);
   });
+  monaco.languages.register({ id: EXPRESSIONS_LANGUAGE_ID });
 }