Prevent spurious tabs by RET in todo-edit-mode (bug#43068)

Prevent spurious tabs by RET in todo-edit-mode (bug#43068)

* lisp/calendar/todo-mode.el (todo-key-bindings-t)
(todo-edit-mode-map): Remove remapping of `newline' to
`newline-and-indent'.
(todo-modes-set-1): Remove local setting of `indent-line-function'.
(todo-edit-mode): Locally set `indent-line-function' to `todo-indent'.

* test/lisp/calendar/todo-mode-tests.el (todo-test-move-item05):
Prevent interactive test failure.  (Until the addition of testcat4
to todo-test-1.todo, the test passed by chance, since testcat3 is
empty and has no archived items.)
(todo-test-edit-item-date-month): Refer to bug number.
(todo-test-multiline-item-indentation-1)
(todo-test-multiline-item-indentation-2)
(todo-test-multiline-item-indentation-3): New tests.

* test/lisp/calendar/todo-mode-resources/todo-test-1.todo: Remove
spurious tabs from testcat1.