Remove workaround - precompilation no longer checks timestamps

Now that we rely solely on checksums to detect outdated precomp files,
we no longer need to ensure that time stamps are different.
Thanks to MasterDuke++ for the reminder.

Author: niner

S10-packages/precompilation.t

@@ -289,9 +289,7 @@ subtest 'precompiled module constants get updated on change' => {
         {:out("pass\n"), :err('')},
     "original content has correct value";
 
-    sleep 2;
     $module.spurt: $module-content.subst: '«VALUE»', '«NEW»';
-    sleep 2;
 
     is_run ｢use RT129266::Bar; say var() eq '«NEW»' ?? 'pass' !! 'fail'｣,
         :compiler-args['-I', 't/spec/packages'],