patch 8.0.1189: E172 is not actually useful

Problem:    E172 is not actually useful, it's only on Unix anyway.
Solution:   Remove the check and the error.
diff --git a/src/version.c b/src/version.c
index 8742035..451eb36 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1189,
+/**/
     1188,
 /**/
     1187,