Update functional tests to use the PSR NullLogger

This avoids using the deprecated NullLogger in tests.

Author: stof

Tests/Functional/app/FirewallEntryPoint/config.yml

@@ -12,7 +12,7 @@ framework:
     profiler: { only_exceptions: false }
 
 services:
-    logger: { class: Symfony\Component\HttpKernel\Log\NullLogger }
+    logger: { class: Psr\Log\NullLogger }
 
 security:
     firewalls:

Tests/Functional/app/config/framework.yml

@@ -12,4 +12,4 @@ framework:
     profiler: { only_exceptions: false }
 
 services:
-    logger: { class: Symfony\Component\HttpKernel\Log\NullLogger }
+    logger: { class: Psr\Log\NullLogger }