Remove the TODO to extract boilerplate code for CreditCardAccessManagerMandatoryReauthFunctionalTest

As discussed offline,
CreditCardAccessManagerMandatoryReauthFunctionalTest doesn't have many
boilerplate codes which can be extracted as a shared function. And the
current tests are already clean enough. Thus, removing the TODO.

Bug: 40935048
Change-Id: I50146a31450759b10f9ef6f3183ef377a9cd88ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6143037
Commit-Queue: Junhui He <junhuihe@google.com>
Reviewed-by: Olivia Saul <jsaul@google.com>
Reviewed-by: Vinny Persky <vinnypersky@google.com>
Cr-Commit-Position: refs/heads/main@{#1402692}