Updating tag value (#15918)

Author: rahuls-microsoft

specification/quota/resource-manager/readme.md

@@ -38,7 +38,7 @@ input-file:
   - Microsoft.Quota/stable/2021-03-15/quota.json
 ```
 
-### Tag: package-021-03-15-preview
+### Tag: package-2021-03-15-preview
 
 These settings apply only when `--tag=package-2021-03-15-preview` is specified on the command line.