With #128051, the default timeline tool changed to
a `sequencer.select` on press with no associated
properties (before, it had `deselect_all`).
This meant that retiming key selection broke (as
reported in #129892) and strips would only deselect
on release if clicking into empty space (due to a separate
keymap item in the global sequencer keymap).
This patch reverts 97e44901b4 while keeping its fix,
in favor of a more robust solution (just add `deselect_all`
to the keymap item properties in the box select tool).
6bd750bc01