delete Search.pm, it's not custom anymore

after upgrade we are now using the 4.2.7 version:

Files /srv/org/wikimedia/bugzilla/Bugzilla/Search.pm and
/root/bugzilla-4.2.7/bugzilla-4.2.7/Bugzilla/Search.pm are identical

the difference between our custom file and the 4.2.4 version was
just adding that 'DISTINCT' in the query that build "my $new_table"

this has been added in the 4.2.7 version anyways, so it was just a
backport.

and one file less that customizes stuff under ./Bugzilla/

RT #5595
RT #5206

Change-Id: I7387d8ac3a7a1443e493cffe818dd26e333a8744