[Settings] Revert CBD dialog dropdown being transactional

Making the clear browsing data dialog dropdown transactional
(crrev.com/c/5249935) had the unintended side effect of the data
counters shown below the data type checkboxes in the dialog's advanced
tab no longer immediately updating from a change to the dropdown
(crbug.com/331925113). The reason: previously, a dropdown change
immediately updated the corresponding pref. The counters monitor those
prefs to compute the new numbers and update the UI. Now, the
transactional dropdowns only write the prefs once the user confirms the
data deletion, which means the dropdown change doesn't reaches the
counters until the deletion is confirmed.

The correct solution to this is to have a dropdown selection change
fire an event to the CPP side to inform the counters. This is being
worked on in crrev.com/c/5425556. As this solution is larger than a
minimal fix for crbug.com/331925113 that can be backmerged, we're first
reverting the dropdowns being transactional (this CL here).

Bug: 331925113
Change-Id: Ie425a5372e9cc0bb1c23d598c0d686de838479e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5428094


Reviewed-by: Martin Šrámek <msramek@chromium.org>
Commit-Queue: Rainhard Findling <rainhard@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283064}