chore: bump bootstrap template to version 19 (#27941)

Bumped the bootstrap template version to 19.

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Author: colifran

packages/aws-cdk/lib/api/bootstrap/bootstrap-template.yaml

@@ -617,7 +617,7 @@ Resources:
       Type: String
       Name:
         Fn::Sub: '/cdk-bootstrap/${Qualifier}/version'
-      Value: '18'
+      Value: '19'
 Outputs:
   BucketName:
     Description: The name of the S3 bucket owned by the CDK toolkit stack