Specification changes / multiple bug fixes

【Contents of the fix】
■Social Button Type 5 (Official Button) “Facebook Like Button” specification change.
■Changed Facebook OGP setting from old specification (fb:admins) to new specification (fb:app_id).
※Please refer to the following article for how to get “fb:app_id” (application ID).
 How to get the fb:app ID required for Facebook OGP settings
■OGP tag optimization
■Fixed an error related to the login judgment in the comment section.
■【macOS Big Sur】Fixed a bug that prevented YouTube video from playing on the top page header content in Chrome browser.
■【Mac】Fixed an issue where the thickness of Japanese and European characters may appear differently when using some fonts.

The following are the files that have been fixed in this update.

【Modified file】
admin/css/editor-style-02.css
admin/inc/basic.php
admin/theme-options.php
comments.php
css/jquery.mb.YTPlayer.min.css
functions/head.php
functions/ogp.php
functions/seo.php
js/jquery.mb.YTPlayer.min.js
languages/ja.mo
languages/ja.po
pagebuilder/assets/css/pagebuilder.css
style.css
template-parts/sns-btn-btm.php
template-parts/sns-btn-top.php

【Deleted files】
admin/inc/backup20180312_blog.php