Tests: Move Hello Dolly test data to match new plugin directory structure.

Moves the Hello Dolly test plugin file from `tests/phpunit/data/plugins/hello.php` to  `tests/phpunit/data/plugins/hello-dolly/hello.php` to match the updated plugin structure in the main codebase.

Fixes failing tests in Tests_Admin_IncludesPlugin that expect the plugin to be located in a hello-dolly directory.

Props jorbin, davidb, afragen.



git-svn-id: https://develop.svn.wordpress.org/trunk@60677 602fd350-edb4-49c9-b593-d223f7449a82

Author: whyisjake