[ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png

PHPBB3-12321
Merge pull request #2198 from n-aleha/ticket/12321

[ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png

* n-aleha/ticket/12321:
  [ticket/12321] Remove execute bit from ucp_main_subscribed.html and buttons.png