Clarify Secret Manager properties are set in bootstrap.properties (#2278)
Clarify Secret Manager properties are set in bootstrap.properties (#2278)

Clarify that secret manager properties are to be added to bootstrap.properties.
spring-cloud/spring-cloud-gcp,GoogleCloudPlatform/spring-cloud-gcp,spring-cloud/spring-cloud-gcp,spring-cloud/spring-cloud-gcp,GoogleCloudPlatform/spring-cloud-gcp,GoogleCloudPlatform/spring-cloud-gcp,spring-cloud/spring-cloud-gcp,GoogleCloudPlatform/spring-cloud-gcp,GoogleCloudPlatform/spring-cloud-gcp