patch 8.2.3823: test for visual replace is in wrong function

Problem:    Test for visual replace is in wrong function.
Solution:   Move it to another function.
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index ed8efc5..e40be5d 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -234,10 +234,6 @@
   call assert_equal("\txaaaa", getline(1))
   set softtabstop&
 
-  call setline(1, "xã̳x")
-  normal gg0lvrb
-  call assert_equal("xbx", getline(1))
-
   enew!
   set noai bs&vim
   if exists('save_t_kD')
@@ -669,6 +665,11 @@
   normal v$rx
   call assert_equal(['x'], getline(1, '$'))
 
+  " replace a character with composing characters
+  call setline(1, "xã̳x")
+  normal gg0lvrb
+  call assert_equal("xbx", getline(1))
+
   bwipe!
 endfunc