Update EN IAM guide.en-gb.md

Changelog:
- Adding a Deny s3:ListAllMyBuckets example

Author: agoude

pages/storage_and_backup/object_storage/s3_identity_and_access_management/guide.en-gb.md

@@ -120,6 +120,24 @@ Some examples of JSON configuration files:
 }
 ```
 
+**Deny listing of all buckets owned by the parent account**
+
+> [!primary]
+>
+> The (`s3:ListAllMyBuckets`) action is allowed by default for a given user. Add the `deny`{.action} effect if you want to explictly refuse the use of the `ListBuckets`{.action} API operation.
+>  
+
+```json
+{
+  "Statement":[{
+    "Sid": "DenyListBucket",
+    "Effect": "Deny",
+    "Action":["s3:ListAllMyBuckets"],
+    "Resource":["*"]
+  }]
+}
+```
+
 **Allow all operations on all project resources**
 
 ```json