patch 8.1.1852: timers test is flaky

Problem:    Timers test is flaky.
Solution:   Accept a larger count.  Add test to list of flaky tests.

src/testdir/runtest.vim

@@ -333,6 +333,7 @@ let s:flaky_tests = [
       \ 'Test_quotestar()',
       \ 'Test_raw_one_time_callback()',
       \ 'Test_reltime()',
+      \ 'Test_repeat_many()',
       \ 'Test_repeat_three()',
       \ 'Test_server_crash()',
       \ 'Test_terminal_ansicolors_default()',

src/testdir/test_timers.vim

@@ -43,7 +43,7 @@ func Test_repeat_many()
   let timer = timer_start(50, 'MyHandler', {'repeat': -1})
   sleep 200m
   call timer_stop(timer)
-  call assert_inrange(2, 4, g:val)
+  call assert_inrange(2, 5, g:val)
 endfunc
 
 func Test_with_partial_callback()

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1852,
 /**/
     1851,
 /**/