doc(promotions): DEVDOCS-6652 update regex to disallow 0.0 value

Author: bc-vincent-zhao

reference/promotions.v3.yml

@@ -1154,7 +1154,7 @@ components:
     MaximumAllowedDiscountAmount:
       type: string
       nullable: true
-      pattern: '^(0|([1-9][0-9]*))(\.[0-9]+)?$'
+      pattern: '^(?!0+(?:\.0+)?$)(\d+)(\.[0-9]+)?$'
       description: |
         The maximum monetary value that can be applied as a discount. It can take value from 1 to 10000000.
         The application of this maximum depends on the discount type: