refactor: remove unused method in test

- Clean up test code by removing an unused method, eliminating the dependency on `jakarta.annotation:jakarta.annotation-api` in this class.

Author: matrei

grails-datastore-gorm/src/test/groovy/grails/gorm/annotation/transactions/TransactionalTransformSpec.groovy

@@ -19,7 +19,6 @@ import org.springframework.util.ReflectionUtils
 import spock.lang.Issue
 import spock.lang.Specification
 
-import jakarta.annotation.PostConstruct
 import javax.sql.DataSource
 /**
  */
@@ -1047,11 +1046,6 @@ class TransactionalTransformSpecService implements InitializingBean {
         return TransactionSynchronizationManager.isActualTransactionActive()
     }
 
-    @PostConstruct
-    public void init() {
-
-    }
-
     @Override
     public void afterPropertiesSet() throws Exception {
         assert !TransactionSynchronizationManager.isActualTransactionActive()