RST: update parser and queries

- The directive type does not longer includes `::`.
- The content of the directives is not longer interpreted as rst,
  but it uses language injection for it.
- Fix a query to allow to capture targets without link.
- Reset the content of the math role so it can be highlighted by the
  injection instead.

Problems I found:

- Capturing the same node with @language and @content will raise an
  error.

  ```
  Error detected while processing FileType Autocommands for "*":
  E5108: Error executing lua /usr/share/nvim/runtime/lua/vim/treesitter/languagetree.lua:331: table index is nil
  ```

  Harcoding the language works, Using the offset predicate doesn't work
  either `(#offset! 0 0 1 0)` nor `(#offset! 0 0 0 5)`

- Generating the grammar using `tree-sitter-cli@0.17.x` breaks
  nvim-treesitter, `@0.16.9` works.

queries/rst/locals.scm

@@ -27,7 +27,7 @@
 ((directive
   name: (type) @_type
   body: (body) @definition)
- (#match? @_type "role::"))
+ (#eq? @_type "role"))
 
 ;; References