patch 8.1.0028: prompt buffer test fails on MS-Windows

Problem:    Prompt buffer test fails on MS-Windows.
Solution:   Disable the test for now. Remove stray assert.
diff --git a/src/version.c b/src/version.c
index 985e659..4d9696b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    28,
+/**/
     27,
 /**/
     26,