Revert breaking change from PR aws-powertools#1846

The PR aws-powertools#1846 added a breaking change to RuleAction which not serializes the enum thus when used as an enum it breaks.

Signed-off-by: royygael <[email protected]>

Author: royygael

Diff for: aws_lambda_powertools/utilities/feature_flags/schema.py

@@ -23,7 +23,7 @@
 HOUR_MIN_SEPARATOR = ":"
 
 
-class RuleAction(Enum):
+class RuleAction(str, Enum):
     EQUALS = "EQUALS"
     NOT_EQUALS = "NOT_EQUALS"
     KEY_GREATER_THAN_VALUE = "KEY_GREATER_THAN_VALUE"