Fix tabsets on Manage Contribution Pages page

On the "Manage Contribution Pages" page, the action links are manipulated with bitwise operations against constants like CRM_Core_Action::VIEW. It relies on the tabset array's keys being a power of 2.

The array_merge I wrapped in a conditional rewrites the array keys to be sequential from 0. This causes the link not to appear, but also removes other links ("Disable" and "Delete").

Because the bitwise operations make it all but impossible to inject a link there, and because it's already not showing up, this PR removes the code so at least "Disable" and "Delete" will show up.