Remove duplicated tests in checkdoc-tests.el

Remove duplicated tests in checkdoc-tests.el

* test/lisp/emacs-lisp/checkdoc-tests.el (checkdoc-cl-defmethod-ok)
(checkdoc-cl-defmethod-with-types-ok, checkdoc-cl-defun-with-key-ok)
(checkdoc-cl-defun-with-allow-other-keys-ok)
(checkdoc-cl-defun-with-default-optional-value-ok)
(checkdoc-cl-defun-with-destructuring-ok): This tests were duplicated,
so keep one copy of them.  Checked by diffing two files with the
suspected tests, and supported by the fact that running occur with the
regexp "^(ert-deftest" reported 14 matches, while the tests being run
were 8.