patch 8.1.1867: still a timer test that is flaky on Mac

Problem:    Still a timer test that is flaky on Mac.
Solution:   Loop with a sleep instead of one fixed sleep.

src/testdir/test_timers.vim

@@ -162,8 +162,16 @@ endfunc
 func Test_timer_stop_in_callback()
   call assert_equal(0, len(timer_info()))
   let g:timer1 = timer_start(10, 'StopTimer1')
-  sleep 50m
-  call assert_equal(0, len(timer_info()))
+  let slept = 0
+  for i in range(10)
+    if len(timer_info()) == 0
+      break
+    endif
+    sleep 10m
+    let slept += 10
+  endfor
+  " This should take only 30 msec, but on Mac it's often longer
+  call assert_inrange(0, 50, slept)
 endfunc
 
 func StopTimerAll(timer)

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1867,
 /**/
     1866,
 /**/