patch 8.1.1854: now another timer test is flaky

Problem:    Now another timer test is flaky.
Solution:   Add test to list of flaky tests.

src/testdir/runtest.vim

@@ -336,6 +336,7 @@ let s:flaky_tests = [
       \ 'Test_repeat_many()',
       \ 'Test_repeat_three()',
       \ 'Test_server_crash()',
+      \ 'Test_stop_all_in_callback()',
       \ 'Test_terminal_ansicolors_default()',
       \ 'Test_terminal_ansicolors_func()',
       \ 'Test_terminal_ansicolors_global()',

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1854,
 /**/
     1853,
 /**/