SSA-006: Fix gradle warnings

[Saklavi]

Following warning can be fixed

`wolty@Legion:~/projekty/secret-santa-app$ ./gradlew clean check --warning-mode all

Task :test
The automatic loading of test framework implementation dependencies has been deprecated. This is scheduled to be removed in Gradle 9.0. Declare the desired test framework directly on the test suite or explicitly declare the test framework implementation dependencies on the test's runtime classpath. Consult the upgrading guide for further information: https://docs.gradle.org/8.4/userguide/upgrading_version_8.html#test_framework_implementation_dependencies

OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended

BUILD SUCCESSFUL in 4s
5 actionable tasks: 5 executed`

spring-io/initializr#1476