patch 8.2.4921: spell test fails because of new illegal byte check

Problem:    Spell test fails because of new illegal byte check.
Solution:   Remove the test.
diff --git a/src/testdir/test_spell.vim b/src/testdir/test_spell.vim
index 94a072e..12f76ef 100644
--- a/src/testdir/test_spell.vim
+++ b/src/testdir/test_spell.vim
@@ -877,14 +877,6 @@
   call delete('XtestSpell')
 endfunc
 
-func Test_spell_single_word()
-  new
-  silent! norm 0R00
-  spell! ßÂ
-  silent 0norm 0r$ Dvz=
-  bwipe!
-endfunc
-
 let g:test_data_aff1 = [
       \"SET ISO8859-1",
       \"TRY esianrtolcdugmphbyfvkwjkqxz-\xEB\xE9\xE8\xEA\xEF\xEE\xE4\xE0\xE2\xF6\xFC\xFB'ESIANRTOLCDUGMPHBYFVKWJKQXZ",
diff --git a/src/version.c b/src/version.c
index fe62555..3183e96 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4921,
+/**/
     4920,
 /**/
     4919,