TypeSet with nested TypeMap shows empty map in plan output when a map is removed from config

### SDK version

```
"v2.0.1" (also tested against v1)
```

### Relevant provider source code
Excerpt from aws/resource_aws_autoscaling_group.go (`v3.7.0`):

```go
"tags": {
Type: schema.TypeSet,
Optional: true,
Elem: &schema.Schema{
Type: schema.TypeMap,
Elem: &schema.Schema{Type: schema.TypeString},
},
```

### Terraform Configuration Files

https://gist.github.com/anGie44/417856ad8231c96a89cf9e0d0356817f

### Debug Output

```
020/09/20 02:02:43 [WARN] Provider "registry.terraform.io/hashicorp/aws" produced an invalid plan for aws_autoscaling_group.bar, but we are tolerating it because it is using the legacy plugin SDK.
The following problems may be the cause of any confusing errors from downstream operations:
- .tags: planned value cty.SetVal([]cty.Value{cty.MapVal(map[string]cty.Value{"key":cty.StringVal("Name"), "propagate_at_launch":cty.StringVal("true"), "value":cty.StringVal("example")}), cty.MapValEmpty(cty.String)}) does not match config value cty.SetVal([]cty.Value{cty.MapVal(map[string]cty.Value{"key":cty.StringVal("Name"), "propagate_at_launch":cty.StringVal("true"), "value":cty.StringVal("example")})}) nor prior value cty.SetVal([]cty.Value{cty.MapVal(map[string]cty.Value{"key":cty.StringVal("Name"), "propagate_at_launch":cty.StringVal("true"), "value":cty.StringVal("example")}), cty.MapVal(map[string]cty.Value{"key":cty.StringVal("Owner"), "propagate_at_launch":cty.StringVal("true"), "value":cty.StringVal("bezos")})})
```
### Expected Behavior
```hcl
~ tags = [
{
"key" = "Name"
"propagate_at_launch" = "true"
"value" = "example"
},
- {
- "key" = "Owner"
- "propagate_at_launch" = "true"
- "value" = "bezos"
},
]
```

### Actual Behavior
```hcl
~ tags = [
{
"key" = "Name"
"propagate_at_launch" = "true"
"value" = "example"
},
- {
- "key" = "Owner"
- "propagate_at_launch" = "true"
- "value" = "bezos"
},
+ {},
]
```

### Steps to Reproduce
1. Using main.tf:
a. `terraform init`
b. `terraform apply`

2. Using update.tf (same as main.tf but with 2nd map in `tags` removed):
a. `terraform plan`

### References
* https://github.com/terraform-providers/terraform-provider-aws/issues/15227

Start by checking go.mod for the SDK version and reproduce the issue with main.tf and update.tf using terraform plan. Trace how the SDK represents the nested TypeSet and TypeMap when the second map is removed. Done means the plan shows only the removed Owner map, without an additional empty map.

Written by the indexing model from the issue text.