Documentation popup links are broken

[sguillia]

The links that appear in the documentation popups are broken.
At least for those documenting the VS Code API.

Steps to Reproduce:

1. Get this vscode demo project in your IDE, open at that line
   https://github.com/microsoft/vscode-extension-samples/blob/0d75c547555a098f8438007c39ca432f819c5354/task-provider-sample/src/customTaskProvider.ts#L95
2. Put your cursor on createFileSystemWatcher
3. Click on a link in the "documentation popup" that appears
4. Observe the error

Version: 1.44.0-insider
Commit: 6cf3dd9
Date: 2020-03-27T05:34:30.255Z
Electron: 7.1.11
Chrome: 78.0.3904.130
Node.js: 12.8.1
V8: 7.8.279.23-electron.0
OS: Linux x64 4.15.0-91-generic

Does this issue occur when all extensions are disabled?: Yes

[mjbvz]

Consequence of using markdown links for our docs.

We'd like to move to standard JS docs for these links. Upstream issue: microsoft/TypeScript#35524

[mjbvz]

Closing this in favor of #120120, which tracks our plan for enabling these links in vscode.d.ts