Text "This plugin is considered deprecated and unsupported." put into short description in readme.txt file

git-svn-id: https://plugins.svn.wordpress.org/oembed-html5-audio/trunk@953565 b8457f37-d9ea-0310-8a92-e5e31aec5664
Text "This plugin is considered deprecated and unsupported." put into short description plugin definition

git-svn-id: https://plugins.svn.wordpress.org/oembed-html5-audio/trunk@953567 b8457f37-d9ea-0310-8a92-e5e31aec5664