patch 8.2.0300: Vim9: expression test fails without channel support

Problem:    Vim9: expression test fails without channel support.
Solution:   Add has('channel') check.

Author: brammool

src/testdir/test_vim9_expr.vim

@@ -773,8 +773,10 @@ def Test_expr7_not()
   assert_equal(true, !{})
   assert_equal(false, !{'yes': 'no'})
 
-  assert_equal(true, !test_null_job())
-  assert_equal(true, !test_null_channel())
+  if has('channel')
+    assert_equal(true, !test_null_job())
+    assert_equal(true, !test_null_channel())
+  endif
 
   assert_equal(true, !test_null_blob())
   assert_equal(true, !0z)

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    300,
 /**/
     299,
 /**/