Don't show clipboard actions for the source app

If the user copies a link from (say) chrome, we don't want to
show an action to open the link back in chrome. This change
suppresses actions where the target package is the same as the
source package.

Bug: 216658864
Test: manual
Change-Id: I4f2ee7ac30b2e54c702e3c9149f77eb5dd5d6243