The treesit-language-at-point function is only suppose to query the
host language.
* lisp/progmodes/elixir-ts-mode.el
(elixir-ts--indent-rules): Add missing rules.
(elixir-ts--treesit-language-at-point): Update function to only query
the host language.
* test/lisp/progmodes/elixir-ts-mode-resources/indent.erts: Add test
for inline docs.
