patch 8.0.1424: the timer_pause test is flaky on Travis

Problem:    The timer_pause test is flaky on Travis.
Solution:   Accept a longer sleep time on Mac.
diff --git a/src/testdir/test_timers.vim b/src/testdir/test_timers.vim
index c8b25c6..55f5245 100644
--- a/src/testdir/test_timers.vim
+++ b/src/testdir/test_timers.vim
@@ -122,7 +122,12 @@
   let slept = WaitFor('g:val == 1')
   call assert_equal(1, g:val)
   if has('reltime')
-    call assert_inrange(0, 30, slept)
+    if has('mac')
+      " The travis Mac machines appear to be very busy.
+      call assert_inrange(0, 40, slept)
+    else
+      call assert_inrange(0, 30, slept)
+    endif
   else
     call assert_inrange(0, 10, slept)
   endif