patch 8.0.1766: expanding abbreviation doesn't work

Problem:    Expanding abbreviation doesn't work. (Tooth Pik)
Solution:   Return OK instead of FALSE and FAIL instead of TRUE. (Christian
            Brabandt)
diff --git a/src/edit.c b/src/edit.c
index f29fbc7..eaf690c 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -10209,9 +10209,9 @@
     int	    i;
 
     if (echeck_abbr(c + ABBR_OFF))
-	return FALSE;
+	return OK;
     if (stop_arrow() == FAIL)
-	return TRUE;
+	return FAIL;
     undisplay_dollar();
 
     /*