semantic validation a github url will cause JSON_PARSING_ERROR

when running `oav validate-spec (a github url for the spec path)`, it will report JSON_PARSING_ERROR

for example:
```
oav validate-spec https://github.com/Azure/autorest.testserver/blob/main/swagger/azure-special-properties.json
Semantically validating https://github.com/Azure/autorest.testserver/blob/main/swagger/azure-special-properties.json

Errors reported:

code: JSON_PARSING_ERROR
message: 'Json parsing error: invalid symbol'
position:
line: 7
column: 1
url: >-
https://github.com/Azure/autorest.testserver/blob/main/swagger/azure-special-properties.json
```

Start by running the `oav validate-spec` command with the GitHub URL shown in the issue and trace how that URL is fetched before semantic validation. Confirm that the downloaded content is parsed as the OpenAPI JSON document rather than producing `JSON_PARSING_ERROR`, then rerun the same example to verify validation proceeds correctly.

Written by the indexing model from the issue text.