test(document): remove redundant global generate_statistics from test config

Stats tracking is already enabled per-test via setStatisticsEnabled(true);
enabling it globally added unnecessary overhead to every test in the suite.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/resources/application-test.yaml

@@ -13,10 +13,6 @@ spring:
     password: test
   mail:
     host: localhost
-  jpa:
-    properties:
-      hibernate:
-        generate_statistics: true
 
 # Disable OTel SDK entirely in tests — prevents auto-configuration from loading resource providers
 # (e.g. AzureAppServiceResourceProvider) that fail against the semconv version used here.