Bug 26449: fix web installer typo

Bug 26449: fix web installer typo

The onboarding segment of the web installer contains a small typo
in Step 4: "Importantl:" (should be "Important:").

This patch fixes that.

Test plan: apply the patch and access the web installer, Step 4 of
the onboarding tool should no longer display the typo.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 5f5e6c85d9d86196da802b2d9155b0d7cafad2da)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>