Issue Type: Bug

When working with tagged template literals in JS and JSX (styled-components is my use case), the backticks used to auto-close when typed, but that recently changed. The big issue though is that if you go into a multi-line literal, and then try to type the closing backtick, vscode inserts two backticks, leaving you with three.

For example if I type:

const Button = styled.button`

I would expect to have the closing tick automatically inserted and the cursor in between them. Instead it just stops there. If I then go on to enter some css and then manually enter the closing backtick, I get:

const Button = styled.button`
  background: papayawhip;
  color: green;
``

I then have to manually delete the third backtick, as if I delete the second, the whole pair is deleted because of the auto-close rules.

I have verified this is happening on Mac and Windows 10, with extensions enabled and disabled, and in the Insiders build.

VS Code version: Code 1.28.1 (3368db6, 2018-10-11T18:07:48.477Z)
OS version: Darwin x64 18.0.0