Bug 34038: Fix incorrect use of __() in .tt and .inc files

Bug 34038: Fix incorrect use of __() in .tt and .inc files

This patch corrects instances of the double-underscore function being
used in .tt and .inc files where the single-underscore function should
be used instead.

To test, apply the patch and update a translation, e.g. fr-FR:

  > cd misc/translator
  > perl translate update fr-FR

- Open the corresponding .po file for JavaScript strings, in this case
  misc/translator/po/fr-FR-staff-prog.po
- Confirm that the strings are now in the .po file for translation. You
  should find these lines:

- koha-tmpl/intranet-tmpl/prog/en/includes/js-biblio-format.inc: "No
  title."
- koha-tmpl/intranet-tmpl/prog/en/modules/catalogue/detail.tt:
  "Check in and add to bundle"
  "Ignore holds and add to bundle"
- koha-tmpl/intranet-tmpl/prog/en/modules/course_reserves/add_items-step1.tt:
  "Please enter only a barcode, or only a biblionumber."
- koha-tmpl/intranet-tmpl/prog/en/modules/course_reserves/batch_add_items.tt:
  "Please enter only barcodes, or only biblionumbers."
- koha-tmpl/intranet-tmpl/prog/en/modules/tools/additional-contents.tt:
  "Please specify a content for 'Default'"

- Check fr-FR-opac-bootstrap.po for these lines:

- koha-tmpl/opac-tmpl/bootstrap/en/includes/calendar.inc:
  "Please enter a valid date (should match %s)."
- koha-tmpl/opac-tmpl/bootstrap/en/modules/opac-basket.tt:
  "No item was selected"
- koha-tmpl/opac-tmpl/bootstrap/en/modules/opac-reserve.tt,
  koha-tmpl/opac-tmpl/bootstrap/en/modules/opac-results.tt,
  koha-tmpl/opac-tmpl/bootstrap/en/modules/opac-shelves.tt:
  "No item was selected"

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>