patch 8.2.3736: test fails without the channel feature

Problem:    Test fails without the channel feature. (Dominique Pellé)
Solution:   Source the check.vim script. (closes #9277)

src/testdir/test_vim9_fails.vim

@@ -1,8 +1,12 @@
 " Test for Vim9 script with failures, causing memory leaks to be reported.
 " The leaks happen after a fork() and can be ignored.
 
+source check.vim
+
 def Test_assignment()
-  if has('channel')
+  if !has('channel')
+    CheckFeature channel
+  else
     var chan1: channel
     var job1: job
     var job2: job = job_start('willfail')

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3736,
 /**/
     3735,
 /**/