revert: "fix($compile): render nested transclusion at the root of a template"

This reverts commit 9d9cdfb575b89e96ae957c986734a49995e2b511.

This commit was causing breakages because of its assumption that transcluded
content would be handled predictably, i.e. with ngTransclude, whereas many
use cases involve manipulating transcluded content in linking functions.