Replace non-interactive span icons with real button elements so
throttle rows can be operated via keyboard and screen readers.
- app/Views/partial/job_throttles.php: swap add_throttle and
remove_throttle spans for <button type="button"> elements,
stripped of default border/background to preserve styling,
with aria-label wired to new language strings.
- app/Language/en/Jobs.php: add add_throttle and remove_throttle
labels used by the new aria-label attributes.
Signed-off-by: objecttothis <17935339+objecttothis@users.noreply.github.com>