patch 8.2.1153: Vim9: script test fails on some systems

Problem:    Vim9: script test fails on some systems.
Solution:   Return proper value from Compare().
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 63da003..c1d7228 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -986,7 +986,7 @@
   let sortlines =<< trim END
       vim9script
       def Compare(i1: number, i2: number): number
-        return 1
+        return i2 - i1
       enddef
 
       export def FastSort(): list<number>