Reveal IDs

Medium risk: 3 removed functions, 2 removed methods, 2 removed constants.

• The function ridwpa_authorplugins_head() was removed. Direct calls from a theme or another plugin will fatal.
• The function ridwpa_authorplugins_init() was removed. Direct calls from a theme or another plugin will fatal.
• The function ridwpa_plugin_footer() was removed. Direct calls from a theme or another plugin will fatal.
• RevealIDsForWPAdmin::add_css() was removed.
• RevealIDsForWPAdmin::require_wpversion_message() was removed.
• The script/style handle os_authorplugins_script is gone. Code that dequeues, or declares a dependency on, that handle is now wrong.
• The constant RIDWPA_VERSION is no longer defined.
• The constant RIDWPAISWP30 is no longer defined.