Clean-up documentation

docs/cheat-sheet.md

@@ -223,7 +223,7 @@ images when used in an `<img/>` tag.
 
 ## Format size
 ```twig
-{{ 12345|format_size() }}
+{{ 12345|format_size }}
 ```
 
 ## Truncate

docs/migration-to-3.x.md

@@ -38,14 +38,14 @@ function preprocess_page(array &$variables): void {
 element. This may break some CSS rules.
 
 Before:
-```HTML
+```html
 <div>
   <div class="from-block-plugin">Block content</div>
 </div>
 ```
 
 After:
-```HTML
+```html
 <div class="from-block-plugin">
   <div>Block content</div>
 </div>