patch 8.1.1706: typo in #ifdef

Problem:    Typo in #ifdef.
Solution:   Change PROT to PROTO.
diff --git a/src/version.c b/src/version.c
index bc8dab7..573f741 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1706,
+/**/
     1705,
 /**/
     1704,