aws_secretsmanager crashes on number value

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#### Overview of the Issue

Storing a numeric value in a plaintext secret in AWS secrets manager crashes packer.
This was found during an upgrade of an old json template which worked fine on packer 1.4.x.

Error returned:

```
Error: Datasource.Execute failed: error to get secret value: "json: cannot unmarshal number into Go value of type map[string]interface {}"

on template.pkr.hcl line 123:
(source code not available)
```

Fix in #10421 does not seem to cover this scenario. json.Valid returns true, but can't unmarshal?

If I try add quotes to my secret value so it stores `"1234"`, I instead get this error:

```
Error: Datasource.Execute failed: error to get secret value: "json: cannot unmarshal string into Go value of type map[string]interface {}"
```

(cannot unmarshal _string_)

#### Reproduction Steps

* Create a plaintext secret named `numeric_plaintext` stored with value `1234`
* Use the secret in a template

### Packer version

Packer v1.10.0

### Simplified Packer Template

```hcl
packer {
required_plugins {
amazon = {
source = "github.com/hashicorp/amazon"
version = ">= 1.3.0"
}
}
}

data "amazon-secretsmanager" "mysecret" {
name = "numeric_plaintext"
}
```

### Operating system and Environment details

macOS

### Log Fragments and crash.log files

-