Bug 10063: Correct documentation of C4::Members::IsMemberBlocked

Bug 10063: Correct documentation of C4::Members::IsMemberBlocked

Rephrased documentation a bit, replacing fine days with the
more general term restriction. As IsDebarred checks for existing
active restrictions.

TEST PLAN
---------
1) apply patch
2) git diff origin/master
   -- do the changes make sense
3) perldoc C4::Members
   -- look for the IsMemberBlocked.
   -- Does it reflect current state
4) koha qa test tools

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>