Bug 24976: Guided report - "Save" button on last step is misleading

Bug 24976: Guided report - "Save" button on last step is misleading

This patch changes the text of the save button on the final step.

To test:

1) Build a guided report (the selections are immaterial)
2) Note that after you have been through the six stages, the button on
the "Confirm custom report" screen should be labelled "Save"
3) Install patch
4) Repeat Step 1. Note that on the "Confirm custom report" screen, the
button is now labelled "Next".
5) Run the report to check that the functionality still works.

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Devinim <kohadevinim@devinim.com.tr>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>