Remove redundant escaping from replacement

Fix for issue: https://github.com/ivaynberg/select2/issues/2251

Summary: seems like replacement string has redundant \\\\ which was not an issue until \\-  is recently added in [abe7777b](https://github.com/ivaynberg/select2/commit/abe7777b0a1cc4b3129c608cc109db53e2f7085b)