Remove unused class "PhutilConsoleConcatenatedView"

Summary:
See D14136. This class is never used anywhere and wouldn't work anyway.

I believe the thing it was intended to do (merging views into a single string) ended up in the base class, PhutilConsoleView.

Test Plan:

• Grepped for PhutilConsoleConcatenatedView in libphutil, Arcanist, and Phabricator.

Reviewers: chad, vrana

Reviewed By: vrana

Differential Revision: https://secure.phabricator.com/D17365