patch 8.1.2151: state test is a bit flaky

Problem:    State test is a bit flaky.
Solution:   Add to the list of flaky tests.

src/testdir/runtest.vim

@@ -341,6 +341,7 @@ let s:flaky_tests = [
       \ 'Test_raw_one_time_callback()',
       \ 'Test_reltime()',
       \ 'Test_server_crash()',
+      \ 'Test_state()',
       \ 'Test_term_mouse_double_click_to_create_tab()',
       \ 'Test_terminal_ansicolors_default()',
       \ 'Test_terminal_ansicolors_func()',

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2151,
 /**/
     2150,
 /**/