correct variable's type, set nullable to false

variables.tf

@@ -459,9 +459,10 @@ variable "zone" {
 
 # tflint-ignore: terraform_unused_declarations
 variable "tracing_tags_enabled" {
-  type        = string
+  type        = bool
   description = "Whether enable tracing tags that generated by BridgeCrew Yor."
   default     = false
+  nullable    = false
 }
 
 # tflint-ignore: terraform_unused_declarations
@@ -469,4 +470,5 @@ variable "tracing_tags_prefix" {
   type        = string
   description = "Default prefix for generated tracing tags"
   default     = "avm_"
+  nullable    = false
 }