extra_window_functions: Remove F-40 from v18 branch

diff --git a/rpm/redhat/18/extra_window_functions/F-40 b/rpm/redhat/18/extra_window_functions/F-40
deleted file mode 120000 (symlink)
index cc7ba0e..0000000
--- a/rpm/redhat/18/extra_window_functions/F-40
+++ /dev/null
@@ -1 +0,0 @@
-../../main/non-common/extra_window_functions/F-40
\ No newline at end of file