patch 8.2.3518: Test_xrestore sometimes fails

Problem:    Test_xrestore sometimes fails.
Solution:   Mark the test as flayky.  Move marking test as flaky to the test
            instead of listing them in runtest.
diff --git a/src/testdir/test_timers.vim b/src/testdir/test_timers.vim
index caeeed6..865a03b 100644
--- a/src/testdir/test_timers.vim
+++ b/src/testdir/test_timers.vim
@@ -16,6 +16,7 @@
 endfunc
 
 func Test_timer_oneshot()
+  let g:test_is_flaky = 1
   let g:val = 0
   let timer = timer_start(50, 'MyHandler')
   let slept = WaitFor('g:val == 1')
@@ -34,6 +35,7 @@
 endfunc
 
 func Test_timer_repeat_three()
+  let g:test_is_flaky = 1
   let g:val = 0
   let timer = timer_start(50, 'MyHandler', {'repeat': 3})
   let slept = WaitFor('g:val == 3')
@@ -51,6 +53,7 @@
 endfunc
 
 func Test_timer_repeat_many()
+  let g:test_is_flaky = 1
   let g:val = 0
   let timer = timer_start(50, 'MyHandler', {'repeat': -1})
   sleep 200m
@@ -64,6 +67,7 @@
 endfunc
 
 func Test_timer_with_partial_callback()
+  let g:test_is_flaky = 1
   let g:val = 0
   let meow = {'one': 1}
   function meow.bite(...)
@@ -127,6 +131,7 @@
 endfunc
 
 func Test_timer_paused()
+  let g:test_is_flaky = 1
   let g:val = 0
 
   let id = timer_start(50, 'MyHandler')
@@ -186,6 +191,7 @@
 endfunc
 
 func Test_timer_stop_in_callback()
+  let g:test_is_flaky = 1
   call assert_equal(0, len(timer_info()))
   let g:timer1 = timer_start(10, 'StopTimer1')
   let slept = 0
@@ -205,6 +211,7 @@
 endfunc
 
 func Test_timer_stop_all_in_callback()
+  let g:test_is_flaky = 1
   call assert_equal(0, len(timer_info()))
   call timer_start(10, 'StopTimerAll')
   call assert_equal(1, len(timer_info()))
@@ -471,4 +478,5 @@
   call delete('XTest_timermessage')
 endfunc
 
+
 " vim: shiftwidth=2 sts=2 expandtab