Bug 23968: fix OPACMySummaryNote feature

Bug 23968: fix OPACMySummaryNote feature

The system preference OPACMySummaryNote is used to display on the logged-in patron summary page at OPAC.
It does not display anymore.

Looks like it comes from code :
[% IF OPACMySummaryNote %][% Koha.Preference('OPACMySummaryNote') | $raw %][% END %]
OPACMySummaryNote used to be a provided variable.

Test plan:
1) Enable system preference OPACMySummaryNote
2) Enter some HTML into it
3) Go to OPAC and loggin
4) Check you see the HTML in opac-user.pl
5) Disable the preference
6) Check you dont see the HTML anymore

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>