setup ts modes in the treesit use-package expression

python-ts-mode and bash-ts-mode are not packages or features, so
we can't use them in a use-package expression.

Since we can't create use-package expressions for them, just set
up the requires variables in the treesit use-package expression.

packages/treesit.el

@@ -1,21 +1,18 @@
 (use-package treesit
-  :if (>= emacs-major-version 29))
+  :if (ignore-errors (treesit-available-p))
+  :mode
+  ((rx (literal ".") "rs" eos) . rust-ts-mode)
+  ((rx (literal ".") "py" eos) . python-ts-mode)
+  ((rx (literal ".") "sh" eos) . bash-ts-mode)
+  :interpreter
+  (("python" "python3" "python2") . python-ts-mode)
+  (("bash" "sh" "openrc-run") . bash-ts-mode))
 
 (use-package rust-ts-mode
     :requires treesit
-    :mode (rx (literal ".") "rs" eos)
-    :hook (rust-ts-mode . (lambda ()
+    :hook
+    (rust-ts-mode . (lambda ()
                       (when (featurep 'rust-mode)
                         (add-hook before-save-hook rust-before-save-method)
                         (add-hook after-save-hook rust-after-save-method)
                         (use-local-map (make-composed-keymap (list rust-ts-mode-map rust-mode-map)))))))
-
-(use-package python-ts-mode
-  :requires treesit
-  :mode (rx (literal ".") "py" eos)
-  :interpreter ("python" "python3" "python2"))
-
-(use-package bash-ts-mode
-  :requires treesit
-  :mode (rx (literal ".") "sh" eos)
-  :interpreter ("bash" "sh" "openrc-run"))