Use the leetcode assessment of test correctness

The code currently decides whether or not the answer is the expected
answer by comparing the `code_answer` and `expected_code_answer`
output blocks in the response to see if they're the same.  This can be
an issue for problems where the output is a list but the problem
specifies that the order doesn't matter.  For instance, for problem
49 (Group Anagrams) the problem states that "You can return the answer
in **any order**."  However, running my solution to that problem gave:

    FAIL:

    Code Answer:
    [["eat","tea","ate"],["tan","nat"],["bat"]]
    [[""]]
    [["a"]]

    Expected Code Answer:
    [["bat"],["nat","tan"],["ate","eat","tea"]]
    [[""]]
    [["a"]]

in the `*leetcode-result-49*` buffer.  The problem here is that the
we're not respecting the order-insensitivity of the answer the problem
specifies.

Looking at the result data structure, we see that there is also a
`correct_answer` field which is the Leetcode assessment of whether the
answer was correct or not.  For example, in the case shown above the
"correct_answer" field is set to "true".

This change uses the "correct_answer" field to decide whether the test
passed or failed, rather than comparing the output blocks directly.

Author: dpkatz

leetcode.el

@@ -1034,7 +1034,7 @@ alist specified in `display-buffer-alist'."
       (goto-char (point-max))
       (cond
        ((eq .status_code 10)
-        (if (equal .code_answer .expected_code_answer)
+        (if (equal .correct_answer t)
             (insert (leetcode--add-font-lock "PASS: " 'leetcode-accepted-face))
           (insert (leetcode--add-font-lock "FAIL: " 'leetcode-error-face)))
         (insert "\n\n")