patch 9.0.0563: timer_info() test fails

Problem:    Timer_info() test fails.
Solution:   Ignore test timeout timer.  Don't use test_null_job() when not
            available.
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index affb958..7698ce8 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -7217,8 +7217,10 @@
     unlet d
     delfunc DictFunc
 
-    call assert_equal(-1, test_refcount(test_null_job()))
-    call assert_equal(-1, test_refcount(test_null_channel()))
+    if has('channel')
+      call assert_equal(-1, test_refcount(test_null_job()))
+      call assert_equal(-1, test_refcount(test_null_channel()))
+    endif
     call assert_equal(-1, test_refcount(test_null_function()))
     call assert_equal(-1, test_refcount(test_null_partial()))
     call assert_equal(-1, test_refcount(test_null_blob()))