Bug 12879: Remove unnecesary diags from Holds.t

Bug 12879: Remove unnecesary diags from Holds.t

There are two unnecessary diag statements:
- Creating biblio instance for testing.
- Creating item instance for testing.

TEST PLAN
---------
1) prove t/db_dependent/Holds.t

t/db_dependent/Holds.t .. 1/38 # Creating biblio instance for testing.
Use of uninitialized value in subroutine entry at /home/tcohen/git/koha-community-src/C4/Charset.pm line 181.
 # Creating item instance for testing.
Use of uninitialized value in subroutine entry at /home/tcohen/git/koha-community-src/C4/Charset.pm line 181.
Use of uninitialized value in subroutine entry at /home/tcohen/git/koha-community-src/C4/Charset.pm line 181.
t/db_dependent/Holds.t .. ok
All tests successful.
Files=1, Tests=38,  1 wallclock secs ( 0.03 usr  0.01 sys +  1.13 cusr  0.11 csys =  1.28 CPU)
Result: PASS

-- They are in the first and fourth lines of this sample output

2) apply patch
3) prove t/db_dependent/Holds.t

t/db_dependent/Holds.t .. 1/38 Use of uninitialized value in subroutine entry at /home/mtompset/kohaclone/C4/Charset.pm line 186.
Use of uninitialized value in subroutine entry at /home/mtompset/kohaclone/C4/Charset.pm line 186.
Use of uninitialized value in subroutine entry at /home/mtompset/kohaclone/C4/Charset.pm line 186.
t/db_dependent/Holds.t .. ok
All tests successful.
Files=1, Tests=38,  1 wallclock secs ( 0.01 usr  0.00 sys +  0.78 cusr  0.09 csys =  0.88 CPU)
Result: PASS

-- They are no longer in the first and fourth lines of this sample output

4) run koha QA test tool

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>