fix: Without create_before_destroy is not possible to rename a subnet_group

[alisson276]

Description

Added

lifecycle {
    create_before_destroy = true
  }

to aws_elasticache_subnet_group.this

Motivation and Context

Tried to rename a subnet_group (because I changed the redis name) and it fails to delete, because it was in-use.
Error:

│ Error: deleting ElastiCache Subnet Group (testing-c3d280ab-2765-b1e7-5be0-bf71f8e80960): operation error ElastiCache: DeleteCacheSubnetGroup, https response error StatusCode: 400, RequestID: b891773d-fc27-40a5-8c77-3af7ecbe6442, CacheSubnetGroupInUse: Cache subnet group testing-c3d280ab-2765-b1e7-5be0-bf71f8e80960 is currently in use by a cache cluster.

Breaking Changes

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

• I have executed pre-commit run -a on my pull request