Improved syntax highlighting for types with "where" in hovers

Generic types in hovers sometimes get expanded like this:

```lua
local foo: t2 where t1 = {
    Connect: (self: t1) -> boolean,
    Destroy: (self: t1) -> boolean,
    Disconnect: (self: t1) -> boolean
} ; t2 = {
    Bar: t1,
}
```

It seems like the `where` breaks syntax highlighting here