patch 8.2.0048: another timers test is flaky on Travis for Mac

Problem:    Another timers test is flaky on Travis for Mac.
Solution:   Increase maximum expected time.
diff --git a/src/testdir/test_timers.vim b/src/testdir/test_timers.vim
index 78676d2..e0d024b 100644
--- a/src/testdir/test_timers.vim
+++ b/src/testdir/test_timers.vim
@@ -73,7 +73,12 @@
   let slept = WaitFor('g:val == 1')
   call assert_equal(1, g:val)
   if has('reltime')
-    call assert_inrange(49, 130, slept)
+    " Mac on Travis can be slow.
+    if has('mac')
+      call assert_inrange(49, 180, slept)
+    else
+      call assert_inrange(49, 130, slept)
+    endif
   else
     call assert_inrange(20, 100, slept)
   endif