doc: _templates: show correct version in sidebar in case of releases

Ensure that version indicator in sidebar is correct in case of releases.

Fixes zephyrproject-rtos/zephyr#91799.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
(cherry picked from commit bbfaf8adec9857a71b4c072d7cdcf66d0ddcf239)
1 file changed