test/timer_spec: relax lower-bound

Test is unreliable on macOS 10.13.  The lower-bound isn't central to the
purpose of the test, so just relax it.

ref https://github.com/neovim/neovim/pull/9095#issuecomment-429603452

> We don't guarantee that a X ms timer is triggered during Y ms sleep
> for any X<Y, though I would expect the load to be really bad for this
> to happen with X=10ms, Y=40ms.

related: #6829

src/nvim/testdir/test_timers.vim

@@ -44,7 +44,7 @@ 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((has('mac') ? 1 : 2), 4, g:val)
 endfunc
 
 func Test_with_partial_callback()
@@ -167,6 +167,9 @@ func Test_stop_all_in_callback()
   let g:timer1 = timer_start(10, 'StopTimerAll')
   let info = timer_info()
   call assert_equal(1, len(info))
+  if has('mac')
+    sleep 100m
+  endif
   sleep 40m
   let info = timer_info()
   call assert_equal(0, len(info))

test/functional/eval/timer_spec.lua

@@ -82,7 +82,7 @@ describe('timers', function()
     run(nil, nil, nil, 300)
     feed("c")
     local count = eval("g:val")
-    assert(count >= 4, 'expected count >= 4, got: '..tostring(count))
+    assert(count >= 3, 'expected count >= 3, got: '..tostring(count))
     eq(99, eval("g:c"))
   end)
 
@@ -144,8 +144,8 @@ describe('timers', function()
     local count2 = eval("g:val")
     -- when count is eval:ed after timer_stop this should be non-racy
     eq(count, count2)
-    assert(4 <= count and count <= 7,
-           'expected (4 <= count <= 7), got: '..tostring(count))
+    assert(3 <= count and count <= 7,
+           'expected (3 <= count <= 7), got: '..tostring(count))
   end)
 
   it('can be stopped from the handler', function()