Bug: aws-sam-cli version 1.80 An invalid OpenApi version was detected

### Description:
openapi.yml
```
openapi: 3.0.3
info:
title: test
description: test
version: 1.0.0
```

I can get the error that

```
$ sam local start-api
Error: An invalid OpenApi version was detected: '', must be one of 2.x or 3.x
make: *** [debug] Error 1
```

### Steps to reproduce:

AWS SAM

### Observed result:

```
Error: An invalid OpenApi version was detected: '', must be one of 2.x or 3.x
```

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

1. OS: mac
2. `sam --version`: SAM CLI, version 1.80.0
3. AWS region: ap-northeast-1

```
{
"version": "1.80.0",
"system": {
"python": "3.8.16",
"os": "macOS-12.3.1-arm64-arm-64bit"
},
"additional_dependencies": {
"docker_engine": "20.10.14",
"aws_cdk": "Not available",
"terraform": "Not available"
}
}
```