r/aws_ecs_service: availability_zone_rebalancing attribute shouldn't …

…have a default

An attributed availability_zone_rebalancing that was introduced in PR #40225
is defined as an optional, but also has a default value. For configurations
where this flag is not defined, plan with `refresh=false` results in
a change that would add this attribute to the state - which is not what
"optional" should mean.

This is to address #40349

internal/service/ecs/service.go

@@ -557,7 +557,6 @@ func resourceService() *schema.Resource {
 			"availability_zone_rebalancing": {
 				Type:             schema.TypeString,
 				Optional:         true,
-				Default:          awstypes.AvailabilityZoneRebalancingDisabled,
 				ValidateDiagFunc: enum.Validate[awstypes.AvailabilityZoneRebalancing](),
 			},
 			names.AttrCapacityProviderStrategy: {