patch 8.1.2404: channel test fails under valgrind

Problem:    Channel test fails under valgrind.
Solution:   Sleep a bit longer.

src/testdir/test_channel.vim

@@ -1860,7 +1860,8 @@ func Test_job_exitval_and_termsig()
   " Terminate job by signal
   let cmd = ['sleep', '10']
   let job = job_start(cmd)
-  sleep 10m
+  " 10m usually works but 50m is needed when running Valgrind
+  sleep 50m
   call job_stop(job)
   call WaitForAssert({-> assert_equal("dead", job_status(job))})
   let info = job_info(job)

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2404,
 /**/
     2403,
 /**/