ctest: Update ctest_submit for CDash behavior change

open.cdash.org was recently upgraded in preparation for the release of
CDash v3.2.0. This upgrade brought a change in behavior where CDash now
responds with HTTP 400 (bad request) rather than HTTP 200 (OK) for MD5
checksum mismatches during submission time.

This commit removes our usage of CURLOPT_FAILONERROR in
cmCTestSubmitHandler.cxx This was necessary to pass along the contents
of the request body ("md5 mismatch") in cases where the web server
(CDash) responds with an error status (400).

Fixes: #25121