patch 8.2.0637: incsearch highlighting does not work for ":sort!"

Problem:    Incsearch highlighting does not work for ":sort!".
Solution:   Skip over the exclamation point. (closes #5983)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index aaa4235..7aaf8db 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1136,11 +1136,14 @@
   " the 'ambiwidth' check.
   sleep 100m
 
-  " Need to send one key at a time to force a redraw.
   call term_sendkeys(buf, ':sort ni u /on')
   call VerifyScreenDump(buf, 'Test_incsearch_sort_01', {})
   call term_sendkeys(buf, "\<Esc>")
 
+  call term_sendkeys(buf, ':sort! /on')
+  call VerifyScreenDump(buf, 'Test_incsearch_sort_02', {})
+  call term_sendkeys(buf, "\<Esc>")
+
   call StopVimInTerminal(buf)
   call delete('Xis_sort_script')
 endfunc