Ignore debian/freeswitch-init.provided_by in git

This is a generated file that was added by commit:

    commit 77f52bb6
    "FS-7928 FS-7618 systemd and package build improvements"

debian/.gitignore

@@ -9,6 +9,7 @@
 /freeswitch-autotools.install
 /freeswitch-mod-*.install
 /freeswitch-conf-*.install
+/freeswitch-init.provided_by
 /freeswitch-lang-*.install
 /freeswitch-music-*.install
 /freeswitch-sounds-*.install