Fix invalid YAML in example in core/state-processors.md and state-providers.md, fixes #2213 (#2223)

Author: xalopp

core/state-processors.md

@@ -324,7 +324,7 @@ If you disabled this feature, you need to register the services by yourself and
 
 services:
     # ...
-    App\State\BlogPostProcessor: ~
+    App\State\BlogPostProcessor:
         tags: [ 'api_platform.state_processor' ]
 
     App\State\UserProcessor:

core/state-providers.md

@@ -404,7 +404,7 @@ To declare the service explicitly, you can use the following snippet:
 
 services:
     # ...
-    App\State\BlogPostProvider: ~
+    App\State\BlogPostProvider:
         tags: [ 'api_platform.state_provider' ]
 
 # api/config/services.yaml