base-files: fix links in banner.failsafe

Update the link to the current section in the documentaion wiki.
This fixes https://github.com/openwrt/packages/issues/6282

Signed-off-by: Sven Roederer <freifunk@it-solutions.geroedel.de>

package/base-files/files/etc/banner.failsafe

@@ -8,6 +8,8 @@ after mount_root:
 * /etc/config		    directory with config files
 
 for more help see:
-http://wiki.openwrt.org/doc/howto/generic.failsafe
+https://openwrt.org/docs/guide-user/troubleshooting/
+- failsafe_and_factory_reset
+- root_password_reset
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