Remove unnecessary use of Time::HiRes from 013_crash_restart.pl.

The regression test 013_crash_restart.pl included "use Time::HiRes qw(usleep)",
but the usleep was not used there.

Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/63ad1368-18e2-8900-8443-524bdfb1bef5@oss.nttdata.com

src/test/recovery/t/013_crash_restart.pl

@@ -17,7 +17,6 @@ use PostgresNode;
 use TestLib;
 use Test::More;
 use Config;
-use Time::HiRes qw(usleep);
 
 plan tests => 18;