Add invisible-island to ncurses source list. (#416)

Remove the dead ftp.vim.org link.

Author: allight

dependency_support/net_invisible_island_ncurses/net_invisible_island_ncurses.bzl

@@ -23,8 +23,8 @@ def net_invisible_island_ncurses():
         name = "net_invisible_island_ncurses",
         urls = [
             "https://ftp.gnu.org/gnu/ncurses/ncurses-6.2.tar.gz",
+            "https://invisible-island.net/archives/ncurses/ncurses-6.2.tar.gz",
             "https://fossies.org/linux/misc/ncurses-6.2.tar.gz",
-            "http://ftp.vim.org/ftp/gnu/ncurses/ncurses-6.2.tar.gz",
         ],
         strip_prefix = "ncurses-6.2",
         sha256 = "30306e0c76e0f9f1f0de987cf1c82a5c21e1ce6568b9227f7da5b71cbea86c9d",