patch 8.2.0300: Vim9: expression test fails without channel support

Problem:    Vim9: expression test fails without channel support.
Solution:   Add has('channel') check.
diff --git a/src/version.c b/src/version.c
index 95a098b..16bf1e1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    300,
+/**/
     299,
 /**/
     298,