patch 8.2.0376: nasty callback test fails on some systems

Problem:    Nasty callback test fails on some systems.
Solution:   Increase the sleep time.
diff --git a/src/version.c b/src/version.c
index 2e720ad..a1a4a88 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    376,
+/**/
     375,
 /**/
     374,