vim-patch:9.0.0019: timers test not run where possible

Problem:    Timers test not run where possible.
Solution:   Adjust platform checks. (closes vim/vim#10645)

eb273cd7b0

Cherry-pick a line from patch 8.2.0183.

src/nvim/testdir/test_timers.vim

@@ -263,8 +263,9 @@ func Interrupt(timer)
 endfunc
 
 func Test_timer_peek_and_get_char()
-  CheckUnix
-  CheckGui
+  if !has('unix') && !has('gui_running')
+    throw 'Skipped: cannot feed low-level input'
+  endif
 
   call timer_start(0, 'FeedAndPeek')
   let intr = timer_start(100, 'Interrupt')
@@ -275,8 +276,9 @@ endfunc
 
 func Test_timer_getchar_zero()
   if has('win32') && !has('gui_running')
-    throw 'Skipped: cannot get low-level input'
+    throw 'Skipped: cannot feed low-level input'
   endif
+  CheckFunction reltimefloat
 
   " Measure the elapsed time to avoid a hang when it fails.
   let start = reltime()