[3.14] gh-148393: Use acquire load for _ma_watcher_tag in dict notify event (gh-14850...

[3.14] gh-148393: Use acquire load for _ma_watcher_tag in dict notify event (gh-148509) (#148512)

The watcher-bits read in _PyDict_NotifyEvent needs to use acquire to
synchronize with the release from PyDict_Watch so that the callback
publication is visible before the callback is invoked.
(cherry picked from commit 19f96f99febe9eadbcc58ffc042791fb017ac90b)

Co-authored-by: Sam Gross <colesbury@gmail.com>