patch 8.1.0591: channel sort test is flaky

Problem:    Channel sort test is flaky.
Solution:   Do not check if the job is running, it may have be done very fast.
diff --git a/src/version.c b/src/version.c
index 3ea9dc6..aafd4cb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    591,
+/**/
     590,
 /**/
     589,