Fix ert-tests.el for the new `handler-bind` code

Fix ert-tests.el for the new `handler-bind` code

Now that `ert.el` uses `handler-bind` instead of `debugger`, some
details of the behavior have changed.  More specifically,
three tests are now broken, but these basically tested the failure
of ERT's machinery to record errors when ERT was run within
a `condition-case`.
AFAICT, these tests do not check for a behavior that we want,
so rather than "fix" them, I deleted them (bug#67862).

* test/lisp/emacs-lisp/ert-tests.el (ert-test-error-debug)
(ert-test-fail-debug-with-condition-case): Delete.
(ert-test-should-failure-debugging): Don't use `ert-debug-on-error`.
(ert-test-with-demoted-errors): It now passes.  Bug#11218 is fixed!