Unable to resolve SSM parameters in AWS::Serverless::Function Layers

### Description:

Unable to resolve SSM parameters in Layers config.

### Steps to reproduce:

```
Hello:
Type: AWS::Serverless::Function
Properties:
CodeUri: dist/
Handler: index.hello
Runtime: nodejs14.x
Layers:
- !Sub '{{resolve:ssm:/layer/common-dependencies:1}}'
```

### Observed result:

```
Error: {{resolve:ssm:/layer/common-dependencies:1}} is an Invalid Layer Arn.

```

### Expected result:

SSM Parameter should be resolved.

### Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: macOS Big Sur
2. `sam --version`: SAM CLI, version 1.16.0
3. AWS region: us-east-1

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