Tap dance callbacks may register weak mods; one case when it happens
is when a tap dance registers a key with modifiers. When the tap
dance is interrupted by pressing another key, these weak mods could
affect the interrupting key (normally any stale weak mods are cleared
at the start of action_exec() when handling a keypress event, but the
tap dance interrupt check code is called later, and the weak mods left
by that code were not cleared). Add another clear_weak_mods() call to
preprocess_tap_dance() to make sure that the interrupting keypress is
not affected by unrelated weak mods from the previous tap dance.
Fixes#12445.
