Added tag for 2025-05-01-preview in readme file

Author: Kanchan Joshi

specification/redisenterprise/resource-manager/readme.md

@@ -26,10 +26,19 @@ These are the global settings for the RedisEnterprise API.
 
 ``` yaml
 openapi-type: arm
-tag: package-2025-04-01
+tag: package-preview-2025-05-01
 ```
 
 
+### Tag: package-preview-2025-05-01-preview
+
+These settings apply only when `--tag=package-preview-2025-05-01-preview` is specified on the command line.
+
+```yaml $(tag) == 'package-preview-2025-05-01-preview'
+input-file:
+  - Microsoft.Cache/preview/2025-05-01-preview/redisenterprise.json
+```
+
 ### Tag: package-2025-04-01
 
 These settings apply only when `--tag=package-2025-04-01` is specified on the command line.