docs: correct mermaid code block formatting

(cherry picked from commit 0770387)

Author: RobinReinecke

adev/src/content/guide/di/defining-dependency-providers.md

@@ -208,7 +208,7 @@ This hierarchy enables:
 
 In Angular, any element with a component or directive can provide values to all of its descendants.
 
-`mermaid
+```mermaid
 graph TD
     subgraph platform
         subgraph root
@@ -218,7 +218,7 @@ graph TD
             C --> D[FriendEntry]
         end
     end
-`
+```
 
 In the example above: