Get rid of `$._raw_js_extension` and `$._raw_ggl_extension`

[nkrkv]

As noted in #143 (comment)

Another simplification that can be made:

There are two rules for extension, $._raw_js_extension and $._raw_ggl_extension. They are used to apply injections highlights but we can do without them.

Example for %re():

(extension_expression
  (extension_identifier) @_name
  (#eq? @_name "re")
  (expression_statement (string ((string_fragment) @regex))))