patch 8.2.4112: function not deleted at end of test

Problem:    Function not deleted at end of test.
Solution:   Delete the function.

src/testdir/test_diffmode.vim

@@ -1212,7 +1212,9 @@ func Test_diff_maintains_change_mark()
   call DiffMaintainsChangeMark()
   set diffopt+=internal
   call DiffMaintainsChangeMark()
+
   set diffopt&
+  delfunc DiffMaintainsChangeMark
 endfunc
 
 " Test for 'patchexpr'

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4112,
 /**/
     4111,
 /**/