patch 8.1.1844: buffer no longer unloaded when adding text properties

Problem:    Buffer no longer unloaded when adding text properties to it.
Solution:   Do not create the memfile. (closes #4808)
diff --git a/src/version.c b/src/version.c
index 5741d5f..f998c52 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1844,
+/**/
     1843,
 /**/
     1842,