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/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,