patch 8.1.1790: :mkvimrc is not tested

Problem:    :mkvimrc is not tested.
Solution:   Add a test.
diff --git a/src/version.c b/src/version.c
index 723a1c1..81f59f9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -774,6 +774,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1790,
+/**/
     1789,
 /**/
     1788,