patch 9.0.1449: test for prompt buffer is flaky

Problem:    Test for prompt buffer is flaky.
Solution:   Use WaitForAssert() instead of TermWait(). (Ozaki Kiichi,
            closes #12247)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1449,
 /**/
     1448,
 /**/