patch 8.0.1370: channel test for callback is flaky

Problem:    Channel test for callback is flaky.
Solution:   Add the test to thelist of flaky tests.
diff --git a/src/version.c b/src/version.c
index 892882f..d7f22b0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1370,
+/**/
     1369,
 /**/
     1368,