Fixes microsoft/vscode#240654: Avoid encoding reserved chars in JSON schema URL

[pedrofrazaopacheco]

Fixes #240654

Title: Prevent percent‑encoding of query parameters when building JSON schema URI

Description:
This change uses skipEncoding in uri.toString(true) to avoid percent‑encoding characters such as :, &, and = when constructing the schema URL. By preserving these characters, the generated URI remains valid and the JSON schema can be successfully retrieved.

Verification:
I deployed a test endpoint at https://vscode-json-bug.vercel.app/ and confirmed that the schema file is reachable only after applying this change.

Reproduction steps:

1. Add the following to your settings.json:

   "json.schemas": [
     {
       "fileMatch": ["associations.config*.json"],
       "url": "https://vscode-json-bug.vercel.app/api/my-file?cmd=readdoc1&downloadid=(9CF9004A-DC3C-746A-97F5-7960CF3BDE0D)&fname=associations.config.schema.json"
     }
   ]

2. Create associations.config.json with {} as its content.
3. Open the Problems panel — there should be no errors loading the schema URL.

Before this change:
Loading failed with:

Unable to load schema from ‘…’: Not Found. The requested location could not be found.

After this change:
The schema URL is valid and loads successfully.

[aeschli]

Thanks @pedrofrazaopacheco that's a good fix!