fix some typescript bg colors in hover window

[mwcz]

When hovering, as with neovim's LSP hover, these groups are displayed with a background color other than Normal's. Because of this, linking to Normal results in the wrong background color. To get around that, I removed the Normal links for typescript groups and linked them to vim-javascript groups instead.

I'm pretty sure there's a better approach that doesn't rely on vim-javascript, I'm just not savvy enough with colorschemes to know what that approach is.

Before:

After:

[cocopon]

Fixed. Thank you for your contribution!