Fix dependency management for spring-boot-testcontainers

This commit adds org.testcontainers:testcontainers as an api dependency
of spring-boot-testcontainers so that GenericContainer can be used
without an additional dependency

See gh-35119

spring-boot-project/spring-boot-testcontainers/build.gradle

@@ -10,6 +10,7 @@ description = "Spring Boot Testcontainers Support"
 
 dependencies {
 	api(project(":spring-boot-project:spring-boot-autoconfigure"))
+	api("org.testcontainers:testcontainers")
 
 	optional("org.springframework:spring-test")
 	optional("org.springframework.data:spring-data-mongodb")