patch 8.2.5074: spell test fails on MS-Windows

Problem:    Spell test fails on MS-Windows.
Solution:   Do not change 'encoding'
diff --git a/src/testdir/test_spell_utf8.vim b/src/testdir/test_spell_utf8.vim
index f9f85a6..fe80689 100644
--- a/src/testdir/test_spell_utf8.vim
+++ b/src/testdir/test_spell_utf8.vim
@@ -811,9 +811,7 @@
   sil! norm P]svc
   norm P]s
 
-  " set 'encoding' to clear the wordt list
-  set enc=latin1
-  set enc=utf-8
+  " TODO: should we clear the word list?
   bwipe!
 endfunc