Bug 42284: (follow-up) Restore hide_marc polarity for marc tag visibility

The original UNLESS/ELSE block kept MARC tag links visible by
default and hid them only when the hide_marc syspref was enabled:

    [% UNLESS Koha.Preference("hide_marc") %]
        toggleMARCTagLinks(true)
    [% ELSE %]
        toggleMARCTagLinks(false);
    [% END %]

The JS port inverted the test without swapping the branches, so
when hide_marc was off the tag links were hidden and when it was
on they were shown -- the opposite of the pref's intent.

Flip the condition back (!Koha.prefs.hide_marc).

To test:
- Set hide_marc = 0: open addbiblio.pl, MARC tag numbers and
  subfield codes are visible on first load.
- Set hide_marc = 1 and clear the marctags cookie (devtools ->
  Application -> Cookies): reload addbiblio.pl, tag numbers and
  subfield codes are hidden on first load.

Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>
Signed-off-by: Jan Kissig <bibliothek@th-wildau.de>
Signed-off-by: Pedro Amorim <pedro.amorim@openfifth.co.uk>

koha-tmpl/intranet-tmpl/prog/en/modules/cataloguing/addbiblio.tt

@@ -168,7 +168,7 @@
         } else if (marctags_cookie == "show") {
             toggleMARCTagLinks(true);
         } else {
-            if (Koha.prefs.hide_marc) {
+            if (!Koha.prefs.hide_marc) {
                 toggleMARCTagLinks(true);
             } else {
                 toggleMARCTagLinks(false);