Fix a spelling mistake in the readme.txt

git-svn-id: https://plugins.svn.wordpress.org/inline-tweet-sharer/trunk@777456 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixed a spelling mistake, and actually uploading it this time.

git-svn-id: https://plugins.svn.wordpress.org/inline-tweet-sharer/trunk@777457 b8457f37-d9ea-0310-8a92-e5e31aec5664