C# Hover Method with // (slash-slash) in constant shows incorrect IntelliSense / Help

Copied from https://github.com/microsoft/vscode-dotnettools/issues/668#, filed by @iJungleboy

### Describe the Issue

When code has `//` characters in the help text then IntelliSense looks broken.


### Steps To Reproduce

Create a `.cs` file like this:

```cs
public class VsCodeBug
{
public void Test(string before, string problem = "see https://xyz.com", string after = null)
{
Test("before");
}
}
```

Then over the call on `Test("before")` and you'll see the what's in the screenshot.

### Expected Behavior

string literals should be self-closing and not bleed out into anything else.

### Environment Information

VS Code 1.83.1